Source: https://pubs.rsc.org/en/content/articlehtml/2019/ob/c8ob02140f
Timestamp: 2019-04-20 04:26:33+00:00

Document:
The present review gives an overview over non-toxic cyanation agents and cyanide sources used in the synthesis of structurally diverse products containing the nitrile function. Nucleophilic as well as electrophilic agents/systems that transfer the entire CN-group were taken in consideration. Reactions in which a preexisting carbon functionality is transformed into a nitrile function by addition of nitrogen are however not covered here.
For chemical companies, the handling of the highly toxic hydrogen cyanide requires closed reactors and substantial safety regulations but is still favored due to cost minimization. For smaller enterprises or research labs, free HCN is often not an option and commercial cyanide sources like metal cyanides, ketone cyanohydrins or trimethylsilyl cyanide are employed instead. Nevertheless, these compounds are still highly toxic and safer alternatives are highly welcome. Over the years, many approaches towards non-toxic alternatives for cyanation reactions have been reported. All these approaches fall into two classes. One class of cyanide sources contains a tightly bound cyano group that needs to be liberated for the reaction to occur. In the other class the cyanide moiety is formed during the reaction from a carbon and a nitrogen atom of any oxidation state.
Several aspects of cyanide sources and cyanating agents have already been discussed in the literature.8 In the focus of these reviews were cyanation reactions with palladium,9,10 copper11,12 or diverse transition metals,13–15 metal free cyanations,16,17 the synthesis of aryl nitriles,18,19 the formation of N/S/O–CN bonds20 or cyanations by C–H activation.21 Here, we intend to give an overview with a particular emphasis on agents that exhibit a low(er) toxicity. Toxic cyanide sources like KCN, NaCN, TMSCN, CuCN, Zn(CN)2, Bu4NCN, malononitriles, DDQ and cyanohydrins are therefore not discussed here.
The first group of non-toxic cyanide sources already contain a CN-group that is tightly bound so that no significant concentrations of cyanide are released from these reagents under normal circumstances. For activation, the X–CN bond needs to be cleaved and the cyanide is transferred to the cyanide acceptor. Depending on the electronegativity of the α-atom and the bonding properties CN-group can be an electrophilic, nucleophilic or radical cyanation agent (Fig. 1).
Fig. 1 Overview of the 1. group of non-toxic sources.
In 1877, Merz and Weith heated ferrocyanide and quartz sand in a furnace and passed a stream of vaporized halobenzene through the mixture. The collected condensate contained the corresponding aryl nitrile. Therefore, Merz and Weith were first to use ferrocyanide as a non-toxic cyanide source for a (nucleophilic) cyanation reaction.22 For a long time, the use of these iron complexes as non-toxic cyanide sources lay dormant until Beller and coworkers rediscovered it in form of an efficient palladium-catalyzed reaction at much lower temperature in 2004 (Scheme 1).23 Since then, a huge variety of reactions have been reported, in particular for the synthesis of aromatic nitriles from aromatic compounds containing a good nucleofuge. The reported reactions can be grouped by their reaction temperature and the catalyst used. For temperatures below 70 °C, two palladium catalyzed processes have been reported by Kwong (2011)24 and by Jian Li (2012).25 Some palladium26–32 and one copper33 catalyzed reaction have been reported to operate below 100 °C while the majority of reactions require higher reaction temperatures. Here, reports with palladium,23,34–62 copper,63–72 a palladium/copper co-catalysis,73,74 and nanoparticles or polymers75–92 can be found.
Scheme 1 Cyanation with ferro-/ferricyanide of aromatic compounds containing a nucleofugic substituent.
Scheme 3 Cyanation of different aromatic compounds with ferro-/ferricyanide.
Nitriles are another compound class containing strongly bound cyano groups. In contrast to the coordinative bonding in metal complexes, a covalent C–C bond prevents the undesired spontaneous liberation of cyanide. Due to the high dissociation energy of this bond, most reactions require harsh conditions to proceed. The first report on the use of nitriles as a cyanide source was published in 1998 by C.-H. Cheng and coworkers (Scheme 4). They described the formation of aromatic nitriles from aryl bromines with benzyl cyanide or acetonitrile with an excess of zinc and in the presence of palladium or nickel catalysts.115 Since 2012, the cyanation with nitriles has moved into the focus of several research groups. In 2012 and 2013, Y. Wang worked on the cyanation with benzyl cyanide and was able to showcase the cyanation of aryl halides by palladium- or copper-catalysis,116,117 as well as the oxidative cyanation of 2-arylpyridines by copper-catalysis using air as terminal oxidant.118 In parallel, a remarkable synthesis of α-amino nitriles from arylamines with benzyl cyanide and tert-butyl hydroperoxide as an oxidant was reported by Wan (2013).119 Even though the oxidant and the cyanide source are still classified as toxic (although they are less dangerous than free cyanide), the oxidative cyanation of amines is standing out from all other syntheses of aromatic nitriles. While the cleavage of a benzylic nitrile function is aided by the benzylic stabilization of reaction intermediates, the activation of aliphatic nitriles is even more challenging. In 2012, the cyanation of aryl iodides with acetonitrile through copper-catalysis in the presence of silver oxide and air was reported by Jin-Heng Li.120 Based on this publication, Jizhen Li extended the reaction to arenediazonium salts in 2015.121 Apart from functionalized arenes carrying a leaving group, unsubstituted aromatic or heteroaromatic compounds can also be cyanated by copper catalysis in the presence of oxygen and N-iodosuccinimide or silver salts. These reactions were reported by C. Zhu in 2013122 and by Shen in 2013 and 2015.123–125 Just recently, the Opatz group described a new strategy to use benzylic and aliphatic nitriles as universal cyanide sources through activation by manganese catalysis. In this reaction, the nitriles were oxidized to their corresponding cyanohydrins with peroxodisulfate and cleaved under acidic conditions to release HCN.113 Another nitrile used for cyanation is the relatively inexpensive ethyl cyanoacetate. This cyanide source has been used by Shen et al. in a palladium-catalysis of aryl halides to yield the aryl nitriles in 2012.126 Diaminomaleonitrile (DAMN, the tetramer of HCN) has also been used as a cyanide source in a palladium-catalysis by Goswami in 2013.127 It should however be noted that the price of DAMN is substantial.
Scheme 4 Cyanation of different compounds with nitriles.
Scheme 5 Cyanation of different compounds with cyanates.
Scheme 6 Cyanation of different compounds with thiocyanates.
Scheme 7 Cyanation of different compounds with tosyl cyanide.
Scheme 8 Cyanation of different compounds with cyanobenziodoxoles.
The more reactive aryl(cyano)iodonium triflates developed by Zhdankin and Stang152,153 have been further studied by Jianbo Wang (2014),154 L. Shi (2015)155 and Studer (2016)156 Unfortunately, they are not yet classified in terms of toxicity and are therefore not discussed in further detail here.
Scheme 9 Cyanation of different compounds with NCTS.
Scheme 10 Cyanation of different compounds with other N–CN sources.
Scheme 11 Cyanation of different compounds with isocyanides.
Scheme 12 Cyanation of different compounds with cyanocarbonyles.
Scheme 13 Cyanation of different compounds with AIBN.
Scheme 14 Cyanation with different cyanide sources.
Some less frequently used cyanating agents can also be found in the literature. Many of them have not yet been assessed toxicologically and are not discussed in detail. These include diethyl phosphorocyanidate (DEPC, classified as toxic), 1-cyano-4-dimethylaminopyridinium bromide (CAP, potential BrCN releasing agent), and cyanoethyl zinc bromide (potential cyanide releasing agent). Surprisingly, the latter reagent is only classified as harmful. Two interesting reagents are N-cyanosuccinimide193 and cyano halo (imidazolium) sulfuranes (analogues to the iodine(III) reagents).194 Although not yet investigated, they might turn out to exhibit acceptable toxicity values in the future.
In the second and smaller group of non-toxic cyanide sources, the cyano group is formed during the reaction itself (Scheme 15). Different oxidation states of the carbon and the nitrogen atom source have been employed.
Scheme 15 Schematic representation of the formation of the cyano group from different carbon and nitrogen sources.
A relatively large group of cyanide sources developed in the last years comprises simple formamides such as DMF or formamide itself. Two major reaction pathways were established for the cyanide formation. In the first case, the cyano carbon originates from the carbonyl group of DMF or formamide and activation with phosphoryl chloride is required. Here, the group of Pelcman described in 1986 the cyanation of electron rich aromatics like indole or veratrole with Viehe's salt, N-(dichloromethylene)dimethyliminium chloride, prepared from DMF (Scheme 16).195 Based on the palladium-catalyzed aminocarbonylation with the Vilsmeier–Haack-reagent, N-(chloromethylene)dimethyliminium phosphorodichloridate, published by Hiyama,196 the group of Bhanage developed palladium- or rhodium-catalyzed nucleophilic cyanations of aryl halides in 2011 and 2013.197,198 By using an analogue of the Vilsmeier reagent synthesized from formamide (N-(chloromethylene)iminium phosphorodichloridate), they were able to achieve a cyanation instead of an amidation.
Scheme 16 Cyanation of different compounds with formamides.
For DMF, a second reaction pathway is also possible. Here, the methyl group functions as the carbon source for the cyanide generation. The nitrogen can either originate from the DMF itself or from an external source. The former pathway has been reported in 2011 by Jiao and coworkers.199 In a complex catalysis using iron(II), palladium(II), and copper(II), they were able to achieve the electrophilic cyanation of indoles or benzofurans. By isotope labeling, they could prove the origin of the carbon and the nitrogen atom forming the cyano group. In a series of papers, palladium or copper catalysis were used to turn DMF in combination with ammonium salts into a binary cyanide source. The groups of Chang (2010–2014) and J. Cheng (2011) were able to apply this procedure to arenes, heteroarenes,200 aryl halides,201,202 arylboronate esters, arylboronic acids,203 and organosilanes.204 Even though the general procedures of all reports are quite similar (oxygen, 130–150 °C and optionally some additives), the protocol is capable of cyanating both electrophilic and nucleophilic starting materials in very high yields.
Scheme 17 Cyanations with miscellaneous cyanide sources.
All reagents and reagent systems described in the present review are less toxic than cyanide itself by definition. They provide additional safety during handling, transportation and often also during their use, while the health risks associated with the respective reagents differ largely. The sources can be subdivided into groups of different toxicity. In the first column of Table 1, sources are listed that are still classified as toxic or at least as harmful. The sources listed in the second column require toxic chemicals for their activation or the overall process. Many of the systems require for their synthesis toxic starting materials such as alkali cyanides or cyanogen halides. These are listed in the third column. Finally, there are reagents or systems that are entirely non-toxic in every way and should be considered as the ideal cyanide sources for future reactions.
I. C. M. Code, Use in mining, https://www.cyanidecode.org/cyanide-facts/use-mining, (accessed 01.05.2018).
T. Willke, Appl. Microbiol. Biotechnol., 2014, 98, 9893–9914 CrossRef CAS.
J. R. Hart, in Ullmann's Encyclopedia of Industrial Chemistry, 2000 Search PubMed.
C. Gousetis and H.-J. Opgenorth, in Ullmann's Encyclopedia of Industrial Chemistry, 2011 Search PubMed.
C. R. Brooks, K. Hacias, R. Hart, D. P. Murphy and M. Petschel, Kirk-Othmer Encyclopedia of Chemical Technology, 1, 2005, vol. 15, pp. 1–34 Search PubMed.
Merkblatt über die besten verfügbaren Techniken für die Herstellung anorganischer Spezialchemikalien, Umweltbundesamt, German Federal Environmental Agency, Dessau, 2007 Search PubMed.
L. D. Pesce, Kirk-Othmer Encyclopedia of Chemical Technology, 1, 2000, vol. 8, pp. 171–199 Search PubMed.
Science of Synthesis, Cross Coupling and Heck-Type Reactions, ed. G. Yan, Y. Zhang and J. Wang, Georg Thieme Verlag KG, Stuttgart, 2013 Search PubMed.
M. Sundermeier, A. Zapf and M. Beller, Eur. J. Inorg. Chem., 2003, 2003, 3513–3526 CrossRef.
P. Anbarasan, T. Schareina and M. Beller, Chem. Soc. Rev., 2011, 40, 5049–5067 RSC.
T. Schareina and M. Beller, in Copper-Mediated Cross-Coupling Reactions, ed. G. Evano and N. Blanchard, Wiley, Weinheim, 2014, ch. 9, pp. 313–334 Search PubMed.
Q. Wen, J. Jin, L. Zhang, Y. Luo, P. Lu and Y. Wang, Tetrahedron Lett., 2014, 55, 1271–1280 CrossRef CAS.
Q. Wen, P. Lu and Y. Wang, RSC Adv., 2014, 4, 47806–47826 RSC.
T. Najam, S. S. A. Shah, K. Mehmood, A. U. Din, S. Rizwan, M. Ashfaq, S. Shaheen and A. Waseem, Inorg. Chim. Acta, 2018, 469, 408–423 CrossRef CAS.
J.-T. Hou, Synlett, 2010, 3115–3116 CrossRef CAS.
J. Schorgenhumer and M. Waser, Org. Chem. Front., 2016, 3, 1535–1540 RSC.
J. Kim, H. J. Kim and S. Chang, Angew. Chem., Int. Ed., 2012, 51, 11948–11959 CrossRef CAS.
G. P. Ellis and T. M. Romney-Alexander, Chem. Rev., 1987, 87, 779–794 CrossRef CAS.
G. Yan, Y. Zhang and J. Wang, Adv. Synth. Catal., 2017, 359, 4068–4105 CrossRef CAS.
J.-T. Yu, F. Teng and J. Cheng, Adv. Synth. Catal., 2016, 359, 26–38 CrossRef.
Y. Ping, Q. Ding and Y. Peng, ACS Catal., 2016, 6, 5989–6005 CrossRef CAS.
V. Merz and W. Weith, Ber. Dtsch. Chem. Ges., 1877, 10, 746–765 CrossRef.
T. Schareina, A. Zapf and M. Beller, Chem. Commun., 2004, 1388–1389 RSC.
P. Y. Yeung, C. P. Tsang and F. Y. Kwong, Tetrahedron Lett., 2011, 52, 7038–7041 CrossRef CAS.
L. Liu, J. Li, J. Xu and J.-t. Sun, Tetrahedron Lett., 2012, 53, 6954–6956 CrossRef CAS.
O. Grossman and D. Gelman, Org. Lett., 2006, 8, 1189–1191 CrossRef CAS.
B. Mariampillai, J. Alliot, M. Li and M. Lautens, J. Am. Chem. Soc., 2007, 129, 15372–15379 CrossRef CAS.
P. Y. Yeung, C. M. So, C. P. Lau and F. Y. Kwong, Org. Lett., 2011, 13, 648–651 CrossRef CAS.
D. Zhang, H. Sun, L. Zhang, Y. Zhou, C. Li, H. Jiang, K. Chen and H. Liu, Chem. Commun., 2012, 48, 2909–2911 RSC.
T. Zou, X. Feng, H. Liu, X. Yu, Y. Yamamoto and M. Bao, RSC Adv., 2013, 3, 20379–20384 RSC.
T. V. Magdesieva, O. M. Nikitin, E. V. Zolotukhina and M. A. Vorotyntsev, Electrochim. Acta, 2014, 122, 289–295 CrossRef CAS.
J. Richardson and S. P. Mutton, J. Org. Chem., 2018, 83, 4922–4931 CrossRef CAS.
G. Guido, F. Marco, O. Werner, L. Frederic, M. Jean and C. Evelina, ChemSusChem, 2014, 7, 919–924 CrossRef.
T. Schareina, A. Zapf and M. Beller, J. Organomet. Chem., 2004, 689, 4576–4583 CrossRef CAS.
Y.-n. Cheng, Z. Duan, T. Li and Y. Wu, Synlett, 2007, 0543–0546 CAS.
S. A. Weissman, D. Zewge and C. Chen, J. Org. Chem., 2005, 70, 1508–1510 CrossRef CAS.
T. Schareina, A. Zapf, W. Mägerlein, N. Müller and M. Beller, Tetrahedron Lett., 2007, 48, 1087–1090 CrossRef CAS.
C. Yi-nan, D. Zheng, L. Ting and W. Yangjie, Lett. Org. Chem., 2007, 4, 352–356 CrossRef.
Y.-Z. Zhu and C. Cai, Aust. J. Chem., 2008, 61, 581–584 CrossRef CAS.
Y.-Z. Zhu and C. Cai, Synth. Commun., 2008, 38, 2753–2760 CrossRef CAS.
S. Velmathi and N. E. Leadbeater, Tetrahedron Lett., 2008, 49, 4693–4694 CrossRef CAS.
T. Schareina, R. Jackstell, T. Schulz, A. Zapf, A. Cotté, M. Gotta and M. Beller, Adv. Synth. Catal., 2009, 351, 643–648 CrossRef CAS.
Y. Ren, Z. Liu, S. He, S. Zhao, J. Wang, R. Niu and W. Yin, Org. Process Res. Dev., 2009, 13, 764–768 CrossRef CAS.
M. Becker, A. Schulz and K. Voss, Synth. Commun., 2011, 41, 1042–1051 CrossRef CAS.
J. Zhang, X. Chen, T. Hu, Y. Zhang, K. Xu, Y. Yu and J. Huang, Catal. Lett., 2010, 139, 56–60 CrossRef CAS.
A. R. Hajipour, K. Karami and A. Pirisedigh, Appl. Organomet. Chem., 2010, 24, 454–457 CrossRef CAS.
J. Schulz, I. Císařová and P. Štěpnička, Organometallics, 2012, 31, 729–738 CrossRef CAS.
A. R. Hajipour, F. Abrisham and G. Tavakoli, Transition Met. Chem., 2011, 36, 725 CrossRef CAS.
A. R. Hajipour, K. Karami, G. Tavakoli and A. Pirisedigh, J. Organomet. Chem., 2011, 696, 819–824 CrossRef CAS.
A. R. Hajipour, F. Rafiee and A. E. Ruoho, Tetrahedron Lett., 2012, 53, 526–529 CrossRef CAS.
R. Gerber, M. Oberholzer and C. M. Frech, Chem. – Eur. J., 2012, 18, 2978–2986 CrossRef CAS.
E. A. Savicheva and V. P. Boyarskiy, Russ. Chem. Bull., 2012, 61, 980–983 CrossRef CAS.
M. Guo, J. Ge, Z. Zhu and X. Wu, Lett. Org. Chem., 2013, 10, 213–215 CrossRef CAS.
E. Kianmehr, H. Hashemi and A. Darvish, Tetrahedron, 2013, 69, 5193–5196 CrossRef CAS.
T. D. Senecal, W. Shu and S. L. Buchwald, Angew. Chem., Int. Ed., 2013, 52, 10035–10039 CrossRef CAS.
A. R. Hajipour and F. Rafiee, J. Iran. Chem. Soc., 2014, 11, 1391–1395 CrossRef CAS.
M. Utsugi, H. Ozawa, E. Toyofuku and M. Hatsuda, Org. Process Res. Dev., 2014, 18, 693–698 CrossRef CAS.
Y. Tu, Y. Zhang, S. Xu, Z. Zhang and X. Xie, Synlett, 2014, 25, 2938–2942 CrossRef CAS.
Z. Xu, Y. Xiao, H. Ding, C. Cao, H. Li, G. Pang and Y. Shi, Synthesis, 2015, 47, 1560–1566 CrossRef CAS.
M. Vafaeezadeh, M. M. Hashemi and M. Karbalaie-Reza, Inorg. Chem. Commun., 2016, 72, 86–90 CrossRef CAS.
B. Majhi and B. C. Ranu, Org. Lett., 2016, 18, 4162–4165 CrossRef CAS.
J. Schulz, F. Horky and P. Stepnicka, Catalysts, 2016, 6, 182 CrossRef.
T. Schareina, A. Zapf and M. Beller, Tetrahedron Lett., 2005, 46, 2585–2588 CrossRef CAS.
Y.-Z. Zhu and C. Cai, J. Chem. Res., 2007, 2007, 484 CrossRef.
T. Schareina, A. Zapf, W. Mägerlein, N. Müller and M. Beller, Chem. – Eur. J., 2007, 13, 6249–6254 CrossRef CAS.
T. Schareina, A. Zapf, A. Cotté, N. Müller and M. Beller, Synthesis, 2008, 3351–3355 CAS.
Y. Ren, Z. Liu, S. Zhao, X. Tian, J. Wang, W. Yin and S. He, Catal. Commun., 2009, 10, 768–771 CrossRef CAS.
Y. Ren, W. Wang, S. Zhao, X. Tian, J. Wang, W. Yin and L. Cheng, Tetrahedron Lett., 2009, 50, 4595–4597 CrossRef CAS.
C. DeBlase and N. E. Leadbeater, Tetrahedron, 2010, 66, 1098–1101 CrossRef CAS.
M. M. Coughlin, C. K. Kelly, S. Lin and A. H. R. MacArthur, Organometallics, 2013, 32, 3537–3543 CrossRef CAS.
S. Bahari and A. Rezaei, Lett. Org. Chem., 2014, 11, 519–523 CrossRef CAS.
S. M. Sajadi and M. Maham, Lett. Org. Chem., 2014, 11, 136–140 CrossRef CAS.
W. Zhou, W. Chen and L. Wang, Org. Biomol. Chem., 2012, 10, 4172–4178 RSC.
X. Tian, Y. Sun, C. Dong, K. Zhang, T. Liang, Y. Zhang and C. Hou, Chem. Lett., 2012, 41, 719–721 CrossRef CAS.
Y. Z. Zhu and C. Cai, Eur. J. Org. Chem., 2007, 2401–2404 CrossRef CAS.
V. Polshettiwar, P. Hesemann and J. J. E. Moreau, Tetrahedron, 2007, 63, 6784–6790 CrossRef CAS.
I. P. Beletskaya, A. V. Selivanova, V. S. Tyurin, V. V. Matveev and A. R. Khokhlov, Russ. J. Org. Chem., 2010, 46, 157–161 CrossRef CAS.
M. Islam, P. Mondal, K. Tuhina, A. S. Roy, S. Mondal and D. Hossain, J. Organomet. Chem., 2010, 695, 2284–2295 CrossRef CAS.
S. M. Islam, P. Mondal, K. Tuhina and S. Roy Anupam, J. Chem. Technol. Biotechnol., 2010, 85, 999–1010 CrossRef CAS.
H. Yu, R. N. Richey, W. D. Miller, J. Xu and S. A. May, J. Org. Chem., 2011, 76, 665–668 CrossRef CAS.
D. Saha, L. Adak, M. Mukherjee and B. C. Ranu, Org. Biomol. Chem., 2012, 10, 952–957 RSC.
I. A. Azath, P. Suresh and K. Pitchumani, New J. Chem., 2012, 36, 2334–2339 RSC.
A. Modak, J. Mondal and A. Bhaumik, Green Chem., 2012, 14, 2840–2855 RSC.
W. Yin, R. Liu, G. He, W. Lv and H. Zhu, RSC Adv., 2014, 4, 37773–37778 RSC.
T. Chatterjee, R. Dey and B. C. Ranu, J. Org. Chem., 2014, 79, 5875–5879 CrossRef CAS.
D. Ganapathy, S. S. Kotha and G. Sekar, Tetrahedron Lett., 2015, 56, 175–178 CrossRef CAS.
B. Suresh Kumar, A. J. Amali and K. Pitchumani, ACS Appl. Mater Interfaces, 2015, 7, 22907–22917 CrossRef CAS.
M. Gholinejad and A. Aminianfar, J. Mol. Catal. A: Chem., 2015, 397, 106–113 CrossRef CAS.
M. Nasrollahzadeh, S. M. Sajadi, A. Rostami-Vartooni and M. Khalaj, J. Colloid Interface Sci., 2015, 453, 237–243 CrossRef CAS.
M. Nasrollahzadeh, Tetrahedron Lett., 2016, 57, 337–339 CrossRef CAS.
M. Nasrollahzadeh and S. M. Sajadi, J. Colloid Interface Sci., 2016, 469, 191–195 CrossRef CAS.
Z.-C. Wu, Q. Yang, X. Ge, Y.-M. Ren, R.-C. Yang and T.-X. Tao, Catal. Lett., 2017, 147, 1333–1338 CrossRef.
Y. Yeung Pui, M. So Chau, P. Lau Chak and Y. Kwong Fuk, Angew. Chem., Int. Ed., 2010, 49, 8918–8922 CrossRef.
C. Zhao, W.-Y. Fang, K. P. Rakesh and H.-L. Qin, Org. Chem. Front., 2018, 5, 1835–1839 RSC.
V. K. Das, S. N. Harsh and N. Karak, Tetrahedron Lett., 2016, 57, 549–553 CrossRef CAS.
M. Nasrollahzadeh, M. Atarod and S. M. Sajadi, J. Colloid Interface Sci., 2017, 486, 153–162 CrossRef CAS.
X. Jia, D. Yang, W. Wang, F. Luo and J. Cheng, J. Org. Chem., 2009, 74, 9470–9474 CrossRef CAS.
G. Yan, C. Kuang, Y. Zhang and J. Wang, Org. Lett., 2010, 12, 1052–1055 CrossRef CAS.
Y. Ren, M. Yan, S. Zhao, J. Wang, J. Ma, X. Tian and W. Yin, Adv. Synth. Catal., 2012, 354, 2301–2308 CrossRef CAS.
For most cited publication in this review we count the number of examples and notify the yield range. However, we excluded examples with yields below 10% or optimization reactions.
Y. Ren, M. Yan, S. Zhao, Y. Sun, J. Wang, W. Yin and Z. Liu, Tetrahedron Lett., 2011, 52, 5107–5109 CrossRef CAS.
Y. Ren, C. Dong, S. Zhao, Y. Sun, J. Wang, J. Ma and C. Hou, Tetrahedron Lett., 2012, 53, 2825–2827 CrossRef CAS.
L. Fu and G. W. Gribble, Org. Lett., 2013, 15, 1622–1625 CrossRef CAS.
X. Hu, R. Li and Z. Li, J. Chem. Res., 2014, 38, 432–436 CrossRef CAS.
A. M. Nauth, N. Otto and T. Opatz, Adv. Synth. Catal., 2015, 357, 3424–3428 CrossRef CAS.
A. M. Nauth, J. C. Orejarena Pacheco, S. Pusch and T. Opatz, Eur. J. Org. Chem., 2017, 6966–6974 CrossRef CAS.
A. Pinto, Y. Jia, L. Neuville and J. Zhu, Chem. – Eur. J., 2007, 13, 961–967 CrossRef CAS.
Z. Zhao and Z. Li, Eur. J. Org. Chem., 2010, 5460–5463 CrossRef CAS.
X. Hu, Z. Zhao and Z. Li, Phosphorus, Sulfur Silicon Relat. Elem., 2012, 187, 1003–1008 CrossRef CAS.
Z. Li, R. Li, H. Zheng, F. Wen, H. Li, J. Yin and J. Yang, J. Brazil. Chem. Soc., 2013, 24, 1739–1743 Search PubMed.
X. Hu, H. Li, J. Yang and Z. Li, Synlett, 2014, 1786–1790 Search PubMed.
Z. Li, J. Yin, T. Li, G. Wen, X. Shen and J. Yang, Tetrahedron, 2014, 70, 5619–5625 CrossRef CAS.
A. M. Nauth, T. Konrad, Z. Papadopulu, N. Vierengel, B. Lipp and T. Opatz, Green Chem., 2018, 20, 4217–4223 RSC.
C. Bolm, R. Mocci, C. Schumacher, M. Turberg, F. Puccetti and G. Hernández José, Angew. Chem., Int. Ed., 2018, 57, 2423–2426 CrossRef CAS.
F.-H. Luo, C.-I. Chu and C.-H. Cheng, Organometallics, 1998, 17, 1025–1030 CrossRef CAS.
Q. Wen, J. Jin, B. Hu, P. Lu and Y. Wang, RSC Adv., 2012, 2, 6167–6169 RSC.
Q. Wen, J. Jin, Y. Mei, P. Lu and Y. Wang, Eur. J. Org. Chem., 2013, 4032–4036 CrossRef CAS.
J. Jin, Q. Wen, P. Lu and Y. Wang, Chem. Commun., 2012, 48, 9933–9935 RSC.
C. Zhang, C. Liu, Y. Shao, X. Bao and X. Wan, Chem. – Eur. J., 2013, 19, 17917–17925 CrossRef CAS.
R.-J. Song, J.-C. Wu, Y. Liu, G.-B. Deng, C.-Y. Wu, W.-T. Wei and J.-H. Li, Synlett, 2012, 23, 2491–2496 CrossRef CAS.
W. Xu, Q. Xu and J. Li, Org. Chem. Front., 2015, 2, 231–235 RSC.
C. Pan, H. Jin, P. Xu, X. Liu, Y. Cheng and C. Zhu, J. Org. Chem., 2013, 78, 9494–9498 CrossRef CAS PubMed.
M. Zhao, W. Zhang and Z. Shen, J. Org. Chem., 2015, 80, 8868–8873 CrossRef CAS PubMed.
Y. Zhu, M. Zhao, W. Lu, L. Li and Z. Shen, Org. Lett., 2015, 17, 2602–2605 CrossRef CAS PubMed.
X. Kou, M. Zhao, X. Qiao, Y. Zhu, X. Tong and Z. Shen, Chem. – Eur. J., 2013, 19, 16880–16886 CrossRef CAS PubMed.
S. Zheng, C. Yu and Z. Shen, Org. Lett., 2012, 14, 3644–3647 CrossRef CAS PubMed.
S. Goswami, A. Manna, A. K. Maity, S. Paul, A. K. Das, M. K. Das, P. Saha, C. K. Quah and H.-K. Fun, Dalton Trans., 2013, 42, 12844–12848 RSC.
K. Buttke, T. Reiher and H. J. Niclas, Synth. Commun., 1992, 22, 2237–2243 CrossRef CAS.
N. Sato, Tetrahedron Lett., 2002, 43, 6403–6404 CrossRef CAS.
N. Sato and Q. Yue, Tetrahedron, 2003, 59, 5831–5836 CrossRef CAS.
R. E. Murray and G. Zweifel, Synthesis, 1980, 150–151 CrossRef CAS.
J.-S. Qiu, Y.-F. Wang, G.-R. Qi, G. Karmaker Pran, H.-Q. Yin and F.-X. Chen, Chem. – Eur. J., 2016, 23, 1775–1778 CrossRef PubMed.
J. Qiu, D. Wu, P. G. Karmaker, G. Qi, P. Chen, H. Yin and F.-X. Chen, Org. Lett., 2017, 19, 4018–4021 CrossRef CAS PubMed.
Y. Tamura, T. Kawasaki, M. Adachi, M. Tanio and Y. Kita, Tetrahedron Lett., 1977, 50, 4417–4420 CrossRef.
W. A. Davis and M. P. Cava, J. Org. Chem., 1983, 48, 2274–2275 CrossRef.
Z. Zhang and L. S. Liebeskind, Org. Lett., 2006, 8, 4331–4333 CrossRef CAS PubMed.
Z. Zhang and L. S. Liebeskind, Synfacts, 2006, 2006, 1270–1270 CrossRef.
G.-Y. Zhang, J.-T. Yu, M.-L. Hu and J. Cheng, J. Org. Chem., 2013, 78, 2710–2714 CrossRef CAS PubMed.
B. K. Vaghasiya, S. P. Satasia, R. P. Thummar, R. D. Kamani, J. R. Avalani, N. H. Sapariya and D. K. Raval, J. Sulfur Chem., 2018, 1–9 Search PubMed.
A. Wagner and A. R. Ofial, J. Org. Chem., 2015, 80, 2848–2854 CrossRef CAS PubMed.
Y. Huang, Y. Yu, Z. Zhu, C. Zhu, J. Cen, X. Li, W. Wu and H. Jiang, J. Org. Chem., 2017, 82, 7621–7627 CrossRef CAS PubMed.
S. Kamijo, T. Hoshikawa and M. Inoue, Org. Lett., 2011, 13, 5928–5931 CrossRef CAS PubMed.
T. Hoshikawa, S. Yoshioka, S. Kamijo and M. Inoue, Synthesis, 2013, 45, 874–887 CrossRef CAS.
R. Akula, Y. Xiong and H. Ibrahim, RSC Adv., 2013, 3, 10731–10735 RSC.
V. V. Zhdankin, C. J. Kuehl, A. P. Krasutsky, J. T. Bolz, B. Mismash, J. K. Woodward and A. J. Simonsen, Tetrahedron Lett., 1995, 36, 7975–7978 CrossRef CAS.
R. Chowdhury, J. Schörgenhumer, J. Novacek and M. Waser, Tetrahedron Lett., 2015, 56, 1911–1914 CrossRef CAS PubMed.
M. Chen, Z.-T. Huang and Q.-Y. Zheng, Org. Biomol. Chem., 2015, 13, 8812–8816 RSC.
B. Ma, X. Lin, L. Lin, X. Feng and X. Liu, J. Org. Chem., 2017, 82, 701–708 CrossRef CAS PubMed.
Y.-F. Wang, J. Qiu, D. Kong, Y. Gao, F. Lu, P. G. Karmaker and F.-X. Chen, Org. Biomol. Chem., 2015, 13, 365–368 RSC.
R. Frei, T. Courant, D. Wodrich Matthew and J. Waser, Chem. – Eur. J., 2014, 21, 2662–2668 CrossRef PubMed.
T. Nagata, H. Matsubara, K. Kiyokawa and S. Minakata, Org. Lett., 2017, 19, 4672–4675 CrossRef CAS PubMed.
P. J. Stang and V. V. Zhdankin, Chem. Rev., 1996, 96, 1123–1178 CrossRef CAS PubMed.
V. V. Zhdankin and P. J. Stang, Chem. Rev., 2002, 102, 2523–2584 CrossRef CAS PubMed.
Z. Shu, W. Ji, X. Wang, Y. Zhou, Y. Zhang and J. Wang, Angew. Chem., Int. Ed., 2014, 53, 2186–2189 CrossRef CAS PubMed.
D. Zhu, D. Chang and L. Shi, Chem. Commun., 2015, 51, 7180–7183 RSC.
X. Wang and A. Studer, J. Am. Chem. Soc., 2016, 138, 2977–2980 CrossRef CAS PubMed.
F. Kurzer, J. Chem. Soc., 1949, 1034–1038 RSC.
F. Kurzer, J. Chem. Soc., 1949, 3029–3033 RSC.
S. Mo, Synlett, 2014, 1337–1338 CAS.
P. Anbarasan, H. Neumann and M. Beller, Chem. – Eur. J., 2011, 17, 4217–4222 CrossRef CAS PubMed.
P. Anbarasan, H. Neumann and M. Beller, Angew. Chem., Int. Ed., 2011, 50, 519–522 CrossRef CAS PubMed.
Y. Yang, Y. Zhang and J. Wang, Org. Lett., 2011, 13, 5608–5611 CrossRef CAS PubMed.
M. Chaitanya, D. Yadagiri and P. Anbarasan, Org. Lett., 2013, 15, 4960–4963 CrossRef CAS PubMed.
D.-G. Yu, T. Gensch, F. de Azambuja, S. Vásquez-Céspedes and F. Glorius, J. Am. Chem. Soc., 2014, 136, 17722–17725 CrossRef CAS PubMed.
Y. Yang and S. L. Buchwald, Angew. Chem., Int. Ed., 2014, 53, 8677–8681 CrossRef CAS PubMed.
Y. Yang and P. Liu, ACS Catal., 2015, 5, 2944–2951 CrossRef CAS.
Y. Cai, X. Qian, A. Rérat, A. Auffrant and C. Gosmini, Adv. Synth. Catal., 2015, 357, 3419–3423 CrossRef CAS.
J. Li, W. Xu, J. Ding and K.-H. Lee, Tetrahedron Lett., 2016, 57, 1205–1209 CrossRef CAS.
K. Kiyokawa, T. Nagata and S. Minakata, Angew. Chem., Int. Ed., 2016, 55, 10458–10462 CrossRef CAS PubMed.
F. Song, R. Salter and L. Chen, J. Org. Chem., 2017, 82, 3530–3537 CrossRef CAS PubMed.
R. Crossley and R. G. Shepherd, J. Chem. Soc., Perkin Trans. 1, 1985, 2479–2481 RSC.
T. V. Hughes, S. D. Hammond and M. P. Cava, J. Org. Chem., 1998, 63, 401–402 CrossRef CAS.
T. V. Hughes and M. P. Cava, J. Org. Chem., 1999, 64, 313–315 CrossRef CAS PubMed.
A. R. Katritzky, R. Akue-Gedu and A. V. Vakulenko, ARKIVOC, 2007, 3, 5–12 Search PubMed.
Y.-q. Wu, D. C. Limburg, D. E. Wilkinson and G. S. Hamilton, Org. Lett., 2000, 2, 795–797 CrossRef CAS PubMed.
P. Anbarasan, H. Neumann and M. Beller, Chem. – Eur. J., 2010, 16, 4725–4728 CrossRef CAS PubMed.
J.-J. Kim, D.-H. Kweon, S.-D. Cho, H.-K. Kim, E.-Y. Jung, S.-G. Lee, J. R. Falck and Y.-J. Yoon, Tetrahedron, 2005, 61, 5889–5894 CrossRef CAS.
S. Xu, X. Huang, X. Hong and B. Xu, Org. Lett., 2012, 14, 4614–4617 CrossRef CAS PubMed.
X. Jiang, J.-M. Wang, Y. Zhang, Z. Chen, Y.-M. Zhu and S.-J. Ji, Tetrahedron, 2015, 71, 4883–4887 CrossRef CAS.
A. Coppola, P. Sánchez-Alonso, D. Sucunza, C. Burgos, R. Alajarín, J. Alvarez-Builla, M. E. G. Mosquera and J. J. Vaquero, Org. Lett., 2013, 15, 3388–3391 CrossRef CAS PubMed.
K. H. V. Reddy, G. Satish, V. P. Reddy, B. S. P. A. Kumar and Y. V. D. Nageswar, RSC Adv., 2012, 2, 11084–11088 RSC.
V. Rao Kasanneni Tirumala, B. Haribabu, S. S. Prasad Potharaju and N. Lingaiah, ChemCatChem, 2012, 4, 1173–1178 CrossRef.
A. Brahma, B. Musio, U. Ismayilova, N. Nikbin, S. B. Kamptmann, P. Siegert, G. E. Jeromin, S. V. Ley and M. Pohl, Synlett, 2016, 27, 262–266 CAS.
J. Vicario, J. M. Ezpeleta and F. Palacios, Adv. Synth. Catal., 2012, 354, 2641–2647 CrossRef CAS.
H. Xu, P.-T. Liu, Y.-H. Li and F.-S. Han, Org. Lett., 2013, 15, 3354–3357 CrossRef CAS PubMed.
F. Teng, J.-T. Yu, H. Yang, Y. Jiang and J. Cheng, Chem. Commun., 2014, 50, 12139–12141 RSC.
F. Teng, J.-T. Yu, Z. Zhou, H. Chu and J. Cheng, J. Org. Chem., 2015, 80, 2822–2826 CrossRef CAS PubMed.
G. Rong, J. Mao, Y. Zheng, R. Yao and X. Xu, Chem. Commun., 2015, 51, 13822–13825 RSC.
P.-Y. Liu, C. Zhang, S.-C. Zhao, F. Yu, F. Li and Y.-P. He, J. Org. Chem., 2017, 82, 12786–12790 CrossRef CAS PubMed.
T. Tajima and A. Nakajima, J. Am. Chem. Soc., 2008, 130, 10496–10497 CrossRef CAS PubMed.
A. Karimi Zarchi Mohammad and N. Ebrahimi, J. Appl. Polym. Sci., 2012, 125, 2163–2169 CrossRef.
R. Takise, K. Itami and J. Yamaguchi, Org. Lett., 2016, 18, 4428–4431 CrossRef CAS PubMed.
A. B. Pawar and S. Chang, Org. Lett., 2015, 17, 660–663 CrossRef CAS PubMed.
G. Talavera, J. Peña and M. Alcarazo, J. Am. Chem. Soc., 2015, 137, 8704–8707 CrossRef CAS PubMed.
J. Bergman and B. Pelcman, Tetrahedron Lett., 1986, 27, 1939–1942 CrossRef CAS.
K. Hosoi, K. Nozaki and T. Hiyama, Org. Lett., 2002, 4, 2849–2851 CrossRef CAS PubMed.
N. Sawant Dinesh, S. Wagh Yogesh, J. Tambade Pawan, D. Bhatte Kushal and M. Bhanage Bhalchandra, Adv. Synth. Catal., 2011, 353, 781–787 CrossRef.
A. B. Khemnar, D. N. Sawant and B. M. Bhanage, Tetrahedron Lett., 2013, 54, 2682–2684 CrossRef CAS.
S. Ding and N. Jiao, J. Am. Chem. Soc., 2011, 133, 12374–12377 CrossRef CAS PubMed.
J. Kim and S. Chang, J. Am. Chem. Soc., 2010, 132, 10272–10274 CrossRef CAS PubMed.
G. Zhang, X. Ren, J. Chen, M. Hu and J. Cheng, Org. Lett., 2011, 13, 5004–5007 CrossRef CAS PubMed.
A. B. Pawar and S. Chang, Chem. Commun., 2014, 50, 448–450 RSC.
J. Kim, J. Choi, K. Shin and S. Chang, J. Am. Chem. Soc., 2012, 134, 2528–2531 CrossRef CAS PubMed.
Z. Wang and S. Chang, Org. Lett., 2013, 15, 1990–1993 CrossRef CAS PubMed.
X. Chen, X.-S. Hao, C. E. Goodhue and J.-Q. Yu, J. Am. Chem. Soc., 2006, 128, 6790–6791 CrossRef CAS PubMed.
X. Ren, J. Chen, F. Chen and J. Cheng, Chem. Commun., 2011, 47, 6725–6727 RSC.
K. Zheng, B. Liu, S. Chen and F. Chen, Tetrahedron Lett., 2013, 54, 5250–5252 CrossRef CAS.
For industrial synthesis from iron salts and HCN.
For synthesis from blood, horn, bone or flesh.

References: V. 
 V. 
 V. 
 V. 

V. 
 V. 
 V. 
 V. 

V. 

V. 
 V. 

V. 
 V. 
 V. 
 V. 
 V. 
 V. 
 V. 

V. 
 V.