bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ring transformations in reactions of heterocyclic compounds with nucleophiles (X). A novel pyrimidine rearrangement reaction
Authors: van der Plas H. C. , Vollering M. C. 
Published: September 2010

AbstractThe ring interconversion of 5‐(1‐hydrazonoethyl)‐2,4‐dimethylpyrimidine into 4‐acetyl‐3‐methylpyrazole azine and of 5‐[1‐(hydroxyimino)ethyl]‐2,4‐dimethylpyrimidine into 5[1‐(hydroxyimino)ethyl]‐3‐methylisoxazole is described. These new ring transformations take place by an attack of the nucleophilic end of the side‐chain at position 5 of the pyrimidine ring to C(6) with simultaneous fission of the N(1)‐C(6) bond.
Chemistry of acetylenic ethers 108 Stereospecific addition of organocopper(I) reagents to 1‐alkynyl sulfones
Authors: Meijer J. , Vermeer P. 
Published: September 2010

Abstract1‐Alkynyl sulfones R1CCSO2‐R2, 1 are very prone to addition of organo‐copper(I) reagents “RCu”. The stereochemistry in the vinylic sulfones RR1CCHSO2‐R2, 2 so produced appeared to be dependent on the relative amounts of copper(I) bromide and the Grignard RMgX (X = Cl, Br) from which the organocopper(I) compound “RCu” was prepared. When an excess of copper(I) bromide was used the addition proved to be almost exclusively a cis‐addition in most cases.
Photoaddition of phenanthraquinone to alkyl‐substituted (alkylthio)acetylenes. Chemistry of acetylenic ethers 109
Authors: Mosterd A. , Lecluijze R.E.L.J. , Bos H.J.T. 
Published: September 2010

AbstractPhotoaddition of phenanthraquinone (1) to alkyl‐substituted (alkylthio)acetylenes (2: R2‐C≡CSR1) affords unsaturated (alkylthio)‐1,4‐diketones (5) formed by [2 + 2]‐cyclo‐addition. By irradiation and by chromatography on alumina these 1,4‐diketones (5) are converted into 2‐hydroxyfuranones (6). Treatment of 5 with tin(II) chloride in acetic acid affords 3‐(alkylthio)phenanthro[9,10‐b]furans (7).
Photochemical cyclo‐addition of 9,10‐phenanthraquinone to phenylallene. Kinetics and temperature effects
Authors: Koster R.J.C. , Bos H.J.T. 
Published: September 2010

AbstractRate constants at various temperatures for the photocyclo‐addition reaction of 9,10‐phenanthraquinone (PQ) with phenylallene (2), were determined in benzene. ΔH≠ = 4.2 kJ.Mol−1 and ΔS≠ = −72 J.Mol−1.K−1 were calculated.Detailed product analysis revealed besides the known type of [4 + 2]‐cyclo‐adducts (dihydrodioxins, 3 and 4), a [2 + 2]‐cyclo‐adduct (oxetane, 5) and a hydrogen abstraction product (6).
Aromatic lead(IV) compounds VI. PMR spectroscopy of para‐substituted aryllead compounds
Authors: de Vos D. , van Der Kooi H.O. , Wolters J. , van Der Gen A. 
Published: September 2010

AbstractPMR data on several series of para‐substituted aryllead compounds are presented. An attempt is made to explain the variation in lead‐proton coupling constants in terms of changes in hybridization and charge on the lead atom.
Photodehydrocyclizations of stilbene‐like compounds XIV Photosynthesis and photoreactions of 1,2‐ and 1,14‐diphenylpentahelicene derivatives
Authors: Laarhoven W.H. , Boumans P.G.F. 
Published: September 2010

AbstractTwo polycyclic aromatics having a phenyl‐substituted pentahelicene moiety, 13,14‐diphenyldibenzo[c,g]chrysene (19) and 14,15‐diphenyldibenzo[f,j]picene (38) have been obtained by irradiation of the appropriate diarylethylenes (13 and 18). Further irradiation of 19 in benzene yields mainly dibenzo[a,g]coronene (21) by cyclodehydrogenation with simultaneous loss of a phenyl substituent. The side products of this reaction are probably formed via rearrangements similar to those previously found during the photoreaction which occurs on irradiation of 1,12‐diphenyltriphenylene. Their most probable structures are 15‐phenyldibenzo[a,g]coronene (28) and 15‐phenyldibenzo[a,ghi]naphtho[2,1,8a,8‐cde]perylene (31). Irradiation of 19 in ethyl acetate yields only 28 (main product) and 31. Photocyclization of 38 could not be effected. NMR data for the cis‐trans isomers of the starting compounds (13 and 18) revealed that the cis isomers exist mainly in the overcrowded syn conformation.
A proton magnetic resonance study of the influence of the solvent on the rotation about the carbamate amide bond in N‐(benzyloxycarbonyl)‐L‐proline t‐butyl ester
Authors: de Leer E.W.B. , van der Toorn J.M. 
Published: September 2010

AbstractThe NMR spectrum of N‐(benzyloxycarbonyl)‐L‐proline t‐butyl ester shows two t‐butyl signals of slowly interconverting syn and anti rotamers. The t‐butyl signals have been assigned to the syn and the anti form by using Eu(fod), as a shift reagent. The thermodynamic parameters ΔG≠, ΔH≠ and ΔS≠ for rotation about the amide bond have been determined by the method of Shanan — Atidi and Bar‐Eli and by complete line shape analysis, in four solvents of different polarity. The results are discussed.
4‐Methylprotoadamant‐4‐en‐2‐one: An unexpected product from the reaction of l‐methyladamantan‐2‐one with sodium azide and methanesulfonic acid
Authors: Peters J.A. , van Der Toorn J.M. , van Bekkum H. 
Published: September 2010

Abstract4‐Methylprotoadamant‐4‐en‐2‐one was isolated from the reaction of 1‐methyladamantan‐2‐one with sodium azide and methanesulfonic acid. A side product of this reaction is probably 4‐methyleneprotoadamantan‐2‐one.
Proton chemical shifts and charge densities
Authors: Kloosterziel H. , Werner M.A. 
Published: September 2010

AbstractFrom the P.M.R. spectra of phenylcyclopentadienide anion and of phenyltropylium cation it is concluded that the proportionality factor between the proton chemical shift and the charge density of 10 ppm per unit charge is not well founded.
Electrochemical reduction of aza‐aromatics. Part V Influence of fluorine substitution on the electron affinities
Authors: van den Ham D. M. W. , Harrison G. F. S. , Spaans A. , van der Meer D. 
Published: September 2010

AbstractThe electrochemical reduction process of fluoro‐substituted aza‐aromatics can well be described by the pattern which is normally postulated for aryl halogenides, i.e. fission of the carbon‐halogen bond. However, the stability of the intermediate mono‐negative ions is generally higher than for the comparable fluoro‐substituted arenes. As an example of this stability, the ESR spectrum of tetrafluoroquinoxaline is given. The half‐wave reduction potentials of the first reduction wave can be related to the electron affinities of the molecules. These electron affinities have been correlated with those obtained by semi‐empirical quantum‐chemical calculations.
Vapour pressure and structure of selenium trioxide
Authors: Bleijerveld R. H. T. , Mijlhoff F. C. 
Published: September 2010

AbstractThe uncertainty about the constitution of the vapour of selenium trioxide has been settled. It is concluded that only tetramer molecules are present. A new value for the heat of sublimation has been found: 17.7 ± 0.8 Kcal/mole Se4O12, as well as for the heat of evaporation: 15.4 ± 0.2 Kcal/mole Se4O12.
Stereoselectivity and proton binding in copper(II) complexes of aspartic acid, glutamic acid and some N‐methyl or N‐benzylhistidine derivatives
Authors: Ritsma J.H. 
Published: September 2010

AbstractStability constants and stereoselective effects are measured for copper(II) complexes with aspartate (asp), glutamate (glut), histidinate (his) and some N‐alkylhistidinate derivatives: N‐methyl‐ (mhis), N,N‐dimethyl‐ (dimhis) and N‐benzylhistidinate (bhis). For the dicarboxylic amino acids the predominant species in solution are CuA, CuHA and CuA2 *; for histidine and its derivatives:CuA, CuHA, CuA2 and CuHA2. By comparison of competition constants (vide infra) it is found that the ligand is bound via its glycine‐locus in all complexes CuHA. For complexes CuHA2, the mono‐protonated ligand, HA, is also bound to copper by its glycine‐locus if A = his and bhis, and mainly so if A = mhis, but, if A = dimhis, HA, possibly, is monodentate and bound to copper by its imidazole group. No stereoselective effects are found in complexes CuA2 for A = asp, glut, his and mhis; for A = dimhis a significant positive effect (i.e. in favour of the meso complex Cu(DA)(LA)) is found, in contrast to the case for A = bhis. In the protonated copper complexes CuHA2, small negative effects are found for A = his, mhis and bhis, but no effect for dimhis.
Détermination de configurations de dérivés styréniques et stilbéniques di‐ et tri‐substitués par résonance magnétique nucléaire
Authors: Doré Jean‐Christophe , Viel Claude 
Published: September 2010

AbstractThe rules of Pascual, which allow one to determine by calculation, a priori, the configuration E or Z of an ethylenic compound, enabled the authors to verify, to reassign or to assign the exact configuration of numerous derivatives of styrene or stilbene carrying different substituents on their double bond carbon atoms.Certain anomalies observed in the case of α,β‐ethylenic ketones in the experimental values and those calculated by the Pascual increments, enabled the authors to attribute these divergencies to the S‐cis or S‐trans conformations and to estimate their relative importance.
The effect of pressure on the base‐catalysed isomerizations of gem‐dimethyl‐ and isopropyl‐cyclohexenes. Part 6
Authors: van Hoboken N. J. , Wiering P. G. , Steinberg H. 
Published: September 2010

AbstractThe isomerization of gem‐dimethylcyclohexenes and of isopropylcyclohexenes in a solution of potassium tert‐butoxide in dimethyl sulfoxide have been studied as a function of temperature (70°‐98°C) and pressures up to 3000 atm. The activation volumes for the proton abstraction reactions are found to be negative (‐18 to‐25 cm3/mole) and are attributed to an electrostriction of the solvated, negatively charged transition state and partly to the negative activation volume for ionization of potassium tert‐butoxide.
Generation of nitroxides with a chloro or nitro substituent in β‐position
Authors: Kayen A. H. M. , Bolsman Th. A. B. M. , de Boer Th. J. 
Published: September 2010

AbstractNitroxides 1 with a chloro or nitro substituent in the ß‐position can be generated by three methods: addition of radicals to gem‐chloro nitroso‐ or gem‐nitro nitroso compounds (reaction 1), addition of chloro‐ or nitroalkyl radicals to nitroso compounds (reaction 2), and addition of atomic chlorine to nitrones (reaction 3). With nitrogen dioxide instead of chlorine, ß‐nitronitroxides cannot be obtained, because NO2 adds to nitrones via oxygen in a presumably charge‐controlled process. The presence of the chloro or nitro substituent in the ß‐position influences the unpaired spin density at nitrogen and thus lowers the nitroxide splitting constant.The ESR signals of the nitroxides 1 clearly show the hyperfine splittings caused by the ß‐substituent. In the presence of nitric oxide, ß‐chloronitroxides cannot be detected and ß‐nitronitroxides only with difficulty.
NMR studies on σ‐adducts of heterocyclic systems with nucleophiles (Part VIII)13C‐NMR data of pyridazines and some of their covalent amination products
Authors: Klinge D. E. , van der Plas H. C. , van Veldhuizen A. 
Published: September 2010

Abstract13C‐NMR data of several 3‐mono‐ and 3,6‐di‐substituted pyridazines, 3‐, 4‐ and 6‐mono‐ and 3,6‐di‐substituted pyridazine 1‐oxides and 4‐nitro‐3,6‐disubstituted pyridazine 1‐oxides are reported. 13C substituent effects of some substituents in the 3‐, 4‐ and 6‐position of the pyridazine ring and that of the N‐oxide function are calculated. The 13C‐NMR spectra of the σ‐adducts of 4‐nitro‐3,6‐disubstituted pyridazine 1‐oxides with liquid ammonia are described.
A stereospecific synthesis of cis‐ and trans‐1‐alkenyl sulfides from 1‐alkynyl sulfides and a copper(I) hydride complex or lithium tetrahydridoaluminate
Authors: Vermeer P. , Meijer J. , Eylander C. , Brandsma L. 
Published: September 2010

Abstract1‐Alkynyl sulfides R1C≡C‐S‐R2 1 are easily converted with a copper(I) hydride complex in tetrahydrofuran into cis‐1‐alkenyl sulfides R1CHCH‐S‐R2 2 in yields >90%. Treatment of compounds 1 with LiAlH4 in the same solvent leads to the isomeric trans‐1‐alkenyl sulfides R1CH CH‐S‐R2 3 in almost quantitative yield.
Reactions of bromoethoxyisoquinolines with potassium amide in liquid ammonia
Authors: Sanders Georgine M. , van Dijk M. , den Hertog H.J. 
Published: September 2010

AbstractOf the six possible isoquinolines with both a bromo and an ethoxy substituent in the pyridine nucleus, all, except 4‐bromo‐3‐ethoxyisoquinoline, react by simple nucleophilic substitution of the bromo atom and, if placed in position 1, of the ethoxy group. 4‐Bromo‐3‐ethoxyisoquinoline yields a complicated reaction mixture, containing in addition to substitution products dehalogenated compounds and at least five different substituted biisoquinolines.
Electron donor‐acceptor cyclophanes II. Synthesis and electron impact induced fragmentation of cyclophanes derived from 1,2:4,5‐benzene‐ or 1,8:4,5‐naphthalene‐tetracarboxylic diimides
Authors: Schroff L. G. , Zsom R. L. J. , van der Weerdt A. J. A. , Schrier P. I. , Geerts J. P. , Nibbering N. M. M. , Verhoeven J. W. , de Boer Th. J. 
Published: September 2010

AbstractThe condensation of amines of the general type H2N‐(CH2)n‐D‐(CH2)m‐NH2 (D is an aromatic system with electron donor properties) with 1,2:4,5‐benzene‐tetracarboxylic dianhydride or with 1,8:4,5‐naphthalene‐tetracarboxylic dianhydride under high dilution conditions is shown to lead to the formation of electron donor(D)‐acceptor(A) cyclophanes of the type magnified image containing the 1,2:4,5‐benzene‐tetracarboxylic diimide or the 1,8:4,5‐naphthalene‐tetracarboxylic diimide group as an electron acceptor.The fragmentation pattern of the cyclophanes upon electron impact is studied and found to agree completely with the proposed structures.
The reactions between 3′‐methyl‐6‐nitrospiro(2H‐1‐benzopyran‐2,2‐benzothiazolines] and 1,1‐bis[4‐(dimethylamino)phenyl]ethylene and the reactions of salicylaldehydes with 1,1‐bis[4‐(dimethylamino)phenyl]propene. A striking effect of an extra methyl group; photochromic chromenes
Authors: Zwanenburg D. J. , Maas Th. A. M. M. 
Published: September 2010

AbstractThe reactions between 1,1‐bis[4‐(dimethylamino)phenyl]ethylene (Michler's ethylene, 4) and 3′‐methyl‐6‐nitrospiro[2H‐1‐benzopyran‐2,2′‐benzothiazoline] (5, which exists in the open merocyanine form3), and its 3‐methyl derivative 10, respectively, were studied. The methyl group in the 3‐position in 10 has a great influence on the reactivity of this spiropyran at the 4‐position; 5 reacts with 4 giving 2,2‐bis[4‐(dimethylamino)phenyl]‐4‐{2,2‐bis[4‐(dimethylamino)phenyl]vinyl}‐6‐nitrochroman (9), whereas no change of the starting products was observed in the reaction of 10 with 4.The same striking effect of an extra methyl group was found in the reaction of salicylaldehydes with 1,1‐bis[4‐(dimethylamino)phenyl]propene (11). In these cases we isolated the 1:1 products, 2,2‐bis‐[4‐(dimethylamino)phenyl]‐3‐methyl‐2H‐chromenes (13) whereas reactions of salicylaldehydes with 1,1‐bis[4‐(dimethylamino)phenyl]ethylene give only 1:2 products.
Beckmann rearrangement of aldoximes catalyzed by transition metal salts: A dehydration‐hydration reaction
Authors: Leusink A. J. , Meerbeek T. G. , Noltes J. G. 
Published: September 2010

AbstractThe Beckmann rearrangement of aldoximes catalyzed by transition metal salts like palladium and nickel acetylacetonates is shown to be a dehydration‐hydration reaction in which the anti‐oxime is converted into nitrile and the nitrile is converted into amide.
Mechanism of the inhibition of autoxidation by thiophenes
Authors: van Tilborg W.J.M. , Smael P. 
Published: September 2010

AbstractThe antioxidant action of thiophenes is shown to be due to a heterolytic decomposition of hydroperoxides effected by SO2 (H2SO4) which is liberated from the thiophene. Thus, the initiation level in an autoxidizing alkylaromatic compound (n‐hexylbenzene) is decreased and the oxidation is further inhibited by phenol, the heterolysis product of the hydroperoxide. At low thiophene concentrations the inhibition is counterbalanced by the low initiation level in such a way that the oxidation continues to proceed at a constant rate. The effect of substituents, of the concentration and of added bases on the antioxidant activity of thiophenes is reported.
Esters β‐thiocétoniques cyclaniques N° 2 Action des organo‐magnésiens sur ces composés
Authors: Paquer D. , Smadja S. 
Published: September 2010

AbstractAlicyclic β‐thioxo esters react with Grignard reagents to give S‐addition, C‐addition and reduction reactions.When the starting material has a five‐membered ring rearrangement reactions take place.
Synthesis of racemic and of (+)‐ and (‐)‐1‐methyldihydrothebainone. (Chemistry of opium alkaloids, Part IV)
Authors: Beyerman H.C. , Buurman E. , Maat L. , Olieman C. 
Published: September 2010

AbstractRacemic 1‐(5‐benzyloxy‐4‐methoxy‐2‐methylbenzyl)‐1,2,3,4‐tetrahydro‐6‐methoxyisoquinoline (rac. 3) was synthesized (Scheme 1). Resolution with (+)‐ and with (‐)‐6,6′‐dinitrobiphenyl‐2,2′‐dicarboxylic acid yielded (‐)‐ and (+)‐3, respectively. By a Birch reduction, followed by N‐formylation, and by acid‐catalysed cyclization, we obtained in high yield racemic, (‐)‐, and (+)‐N‐formyl‐1‐methylnordihydrothebainone (6), respectively. In two ways, by direct reduction and by deformylation followed by reductive methylation, 6 could be converted selectively into racemic, and (‐)‐, and (+)‐1‐methyldihydrothebainone (7).Synthetic (‐)‐7 was found to be identical with (‐)‐1‐methyldihydrothebainone prepared from natural material. This completes the proof of the structure.The optical rotatory dispersion spectra are discussed.
Preparation, structure and properties of dicopper tris(N,N‐dialkyldithiocarbamato)dihalogeno compounds, Cu2(R2dtc)3X2, with copper in the oxidation states II and III
Authors: van de Leemput P. J. H. A. M. , Cras J.A. , Willemse J. , Beurskens Paul T. , Menger E. 
Published: September 2010

AbstractThe preparation, some magnetic and spectral properties of the compounds Cu2(R2dtc)3X2* (R = Me and Et, X = Br; R = Me, X = Cl) and the crystal structure of Cu2(Et2dtc)3Br2 are reported.The compound, crystallizing in the monoclinic space group Cc [α = 14.421(15), b = 12.980(17), c = 15.152(11) Å and β = 106.82(8)°], contains four formula units per unit cell. The structure, which was refined to a conventional R value of 0.06 for 724 independent non‐zero reflections, consists of chains of alternating Cu(Et2dtc)2 and Cu(Et2dtc)Br2 units, both with copper in a distorted octahedral coordination.The copper atom in the former unit has Cu‐S distances of 2.16(2), 2.20(2), 2.19(2), 2.26(2) and 3.27(3) Å and a Cu‐Br distance of 2.97(2) Å; the copper atom in the latter unit has Cu‐S distances of 2.27(2), 2.29(2), 2.94(4) and 3.00(3) Å and Cu‐Br distances of 2.40(2) Å. These distances suggest the compound to be composed of [Cu(III)(Et2dtc)2]+ and [Cu(II)(Et2dtc)Br2]− ions. The two C‐N and Cu‐S stretching frequencies are in accord with the presence of both Cu(III) and Cu(II).
Addition and substitution reactions of arylthio, arylsulfinyl and arylsulfonyl substituted sulfines with thiols
Authors: Veenstra G.E. , Zwanenburg B. 
Published: September 2010

AbstractStepwise oxidation ofp‐tolylp‐methoxydithiobenzoate (1) gives the sulfines (thione oxides) AnC(=S=O)STol (2), AnC(=S=O)SOTol (3) and AnC(=S=O)SO2Tol (4) (An =p‐CH3OC6H4and Tol =p‐CH3C6H4). Reaction of2withp‐toluenethiol (TolSH) in the presence of Et3N furnishes AnCH(STol)SSTol (5). The sulfine4yields with TolSH/Et3N5and AnCH2SO2Tol (6), with EtSH/Et3N AnCH(SEt)SSEt (7) and witht‐BuSH/Et3N the sulfone6. The sulfine3gives with TolSH/Et3N 5 and witht‐BuSH/Et3N6. In the presence of ZnCl2all three sulfines give rise to deoxygenated products,viz. dithioesters like1and AnCSSEt (8). In the absence of a catalyst, sulfine2, with TolSH and EtSH, undergoes deoxygenation to dithioesters.Sulfine4gave with EtSH the dithioester8as the principal product, whereas with TolSH besides1and5the compound AnCH(SO2Tol)SSTol (9) was obtained. From sulfine3products were obtained that point to a disproportionation into2and4prior to the reaction of thiol with the sulfine function. In the discussion, a rationale is presented for the reactions observed. It is shown that nucleophilic attack of thiol or thiolate anion may occur at the sulfine sulfur as well as the sulfine carbon atom. In the presence of Et3N both reaction modes take place, whereas in the presence of ZnCl2attack at the sulfur seems to dominate.
A facile approach to an optically active tetracyclic intermediate for the synthesis of 6‐methyl‐19‐norsteroids
Authors: Pandit U.K. , Bieräugel H. 
Published: September 2010

AbstractThe asymmetric synthesis of (‐)‐(13S, 17S)‐6‐methyl‐17β‐acetoxy‐13,14‐dehydroequilinin methyl ether is described.
Stereochemistry of cyclopropane ring hydrogenolysis
Authors: Kieboom A.P.G. , van Benschop H.J. , van Bekkum H. 
Published: September 2010

AbstractThe hydrogenolysis of cis‐1,2‐dimethyl‐1,2‐diphenylcyclopropane (cis‐1) has been studied using palladium, platinum, rhodium and Raney‐nickel as catalysts. The stereoselectivity towards suprafacial hydrogen addition to the C(1)−C(2) bond is higher than that for the corresponding trans‐compound (trans‐1), whereas the stereochemistry of the reaction of cis‐1 on palladium is not influenced by strong acids (in contrast to trans‐1).The different behaviour is explained in terms of serious steric repulsion of intermediate species and points to the occurrence of a protonated cyclopropane species in the hydrogenolysis of trans‐1 in acidic medium.
Addition of hydrogen chloride to 1,2,3‐pentatriene
Authors: Mirejovsky D. , Arens J.F. , Drenth W. 
Published: September 2010

AbstractThe addition of HCl to 1,2,3‐pentatriene has been studied in 95 vol. % aqueous ethanol containing 4−10 mol/1 HCl. The reaction involves rate‐determining proton attack at the terminal methylene group with formation of 1,2‐ and 1,4‐adducts. Subsequently, the 1,2‐adduct is converted into a di‐adduct. The reaction shows pseudo‐first‐order kinetics. Log k1 is linear in H0 with a slope equal to −1.18 ± 0.01. The average value of the kinetic isotope effect kH/kD is 1.7. A change in nucleophile (ClO4−, SO24−, Br−) does not affect the rate. The addition of HCl is a two‐step process with a carbocation intermediate. In all probability, alcohol and water are not covalently present in the transition state of the rate‐determining step.
Vinyl copper(I) compounds: Part II: Stereospecific addition of homocuprates to 1‐alkynes in tetrahydrofuran
Authors: Westmijze H. , Meijer J. , Bos H.J.T. , Vermeer P. 
Published: September 2010

AbstractHomocuprates [RCuR”]MgX, 1 (R = alkyl; R” = R or BuC≡C) appeared to be useful reagents for the introduction of an R group into 1‐alkynes R′−C≡C−H 2 (R′ = Ph, H, alkyl) in tetrahydrofuran as a solvent. Depending on R and R′ terminal alkenes RR′CCH2 4a, non‐terminal alkenes E−R′CHCHR 4b or mixtures of 4a and 4b were isolated after protic work‐up. Except for the reaction of t‐Bu2CuMgCl with Ph−C≡C−H and t‐Bu−C≡C−H only cis additions were observed.In two cases, viz. for the reaction of Me2CuMgCl and t‐Bu2CuMgCl with Ph−C≡C−H, evidence was obtained for accompanying proton abstraction from the terminal alkyne 2 by the cuprate. This proton abstraction could be suppressed completely by carrying out the addition in the presence of LiBr. Moreover, a strong accelerating influence of LiBr on the rate of the R transfer from the cuprate 1 to the 1‐alkyne 2 was observed.