text stringlengths 4 7.07k | text_hash stringlengths 32 32 | __index_level_0__ int64 1 1.81M |
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The ship 's primary armament consisted of four 30 @.@ 5 cm ( 12 in ) 45 @-@ caliber guns in two twin gun turrets . This was augmented by a heavy secondary battery of eight 24 cm ( 9 @.@ 4 in ) guns in four wing turrets . The tertiary battery consisted of twenty 10 cm L / 50 guns in casemated single mounts , four 47 mm... | a4d3a7f03e461c3109e56b3be1c94fc7 | 923 |
= = Service history = =
| 23e5a754ef5bf8e29b4df264b6ec61aa | 925 |
The ship was assigned to the Austro @-@ Hungarian Fleet 's 1st Battle Squadron after her 1911 commissioning . In 1912 , Zrínyi and her two sister ships conducted two training cruises into the eastern Mediterranean Sea . On the second cruise into the Aegean Sea , conducted from November to December , Zrínyi and her sis... | bffc9fbfc12183046aecbf2887706e0d | 927 |
In 1913 , Zrínyi participated in an international naval demonstration in the Ionian Sea to protest the Balkan Wars . Ships from other navies included in the demonstration were the British pre @-@ dreadnought HMS King Edward VII , the Italian pre @-@ dreadnought Ammiraglio di Saint Bon , the French armored cruiser Edga... | 30c0625193e2162e211e855f5967da9b | 928 |
During that year , the first of four new dreadnoughts , SMS Viribus Unitis , that made up the Tegetthoff class — the only dreadnoughts built for the Austro @-@ Hungarian Navy — came into active service . With the commissioning of these dreadnoughts , Zrínyi and her sisters were moved from the 1st Division to the 2nd D... | f6e6187e42564a93124e5d37a02e23c0 | 929 |
= = = World War I = = =
| fa3b798e169c5288b7355decab5f85c6 | 931 |
At that time of the assassination of Archduke Franz Ferdinand of Austria on 28 June 1914 , the battleships in the Austro @-@ Hungarian Navy consisted of the Radetzky class , the Tegetthoff class ( which still had one ship , SMS Szent István , under construction ) , the Erzherzog Karl class and finally , the older Habs... | b0c93978ff64813a2d309a8885eb2e23 | 933 |
On 23 May 1915 , between two and four hours after news of the Italian declaration of war reached the main Austro @-@ Hungarian naval base at Pola , Zrínyi and the rest of the fleet departed to bombard the Italian and Montenegrin coast . Their focus was on the important naval base at Ancona , and later the coast of Mon... | 7ea55a0e19e7dbf0a82cbadd907554dc | 934 |
The objective of the bombardment of Ancona was to delay the Italian Army from deploying its forces along the border with Austria @-@ Hungary by destroying critical transportation systems . The surprise attack on Ancona succeeded in delaying the Italian deployment to the Alps for two weeks . This delay gave Austria @-@... | dc4c66dc9134943e02861f5f9d55ae9d | 935 |
Aside from the attack on Ancona , the Austro @-@ Hungarian battleships were largely confined to Pola for the duration of the war . Their operations were limited by Admiral Anton Haus , the commander of the Austro @-@ Hungarian Navy , who believed that he would need to husband his ships to counter any Italian attempt t... | fa7064212ec6e99faaa8cc5a3116a8a9 | 936 |
= = = Post @-@ war fate = = =
| 7f78e04db3284d9b75ecf921f50107d3 | 938 |
After the Austro @-@ Hungarian Empire collapsed in 1918 , the Austrians wanted to turn the fleet over to the newly created State of Slovenes , Croats and Serbs ( later to become a part of the Kingdom of Yugoslavia ) in order to prevent the Italians from claiming the ships as spoils of war . However , the victorious Al... | 31f451a5121df6460f6ba8551d2aafa5 | 940 |
On the morning of 7 November 1920 , Zrínyi was decommissioned . USS Chattanooga took her in tow and , assisted by Brooks and Hovey , towed the battleship to Italy . Under the terms of the treaties of Versailles and St. Germain , Zrínyi was ultimately turned over to the Italian government at Venice . She was broken up ... | e1a0cfc8dae1007dc8d889743fbe54d1 | 941 |
= Geopyxis carbonaria =
| fcfc515212be8f10cc973b0a13f6e287 | 944 |
Geopyxis carbonaria is a species of fungus in the genus Geopyxis , family Pyronemataceae . First described to science in 1805 , and given its current name in 1889 , the species is commonly known as the charcoal loving elf @-@ cup , dwarf acorn cup , stalked bonfire cup , or pixie cup . The small , goblet @-@ shaped fr... | 4da19e454d8c6d265880b83c93aca44f | 946 |
= = Taxonomy = =
| ecc91bdacd3691ba81b1bebd7a833abe | 948 |
The fungus was first described scientifically in 1805 by Johannes Baptista von Albertini and Lewis David de Schweinitz as Peziza carbonaria . Mordecai Cubitt Cooke illustrated the fruitbodies , spores , and asci in his 1879 work Mycographia , seu Icones fungorum . Figures of fungi from all parts of the world . In 1889... | 40595a03aa042a04a9ae3f68c323e607 | 950 |
The specific epithet carbonaria derives from the Latin word for " charcoal " . Common names given to the fungus include " charcoal loving elf @-@ cup " , " dwarf acorn cup " , " pixie cup " , and the British Mycological Society approved " stalked bonfire cup " .
| 9e7f85d0b0c59f7048491420e4ba79e5 | 951 |
= = Description = =
| 7096d9cc91723f919ab4f5acdab6bccb | 953 |
The fruitbodies ( ascocarps ) of Geopyxis carbonaris are cup shaped , 1 – 2 cm wide , and have fringed whitish margins . The inner spore @-@ bearing surface of the cup , the hymenium , is brick red and smooth , while the exterior surface is a dull yellow , and may be either smooth or have blister @-@ like spots ( pust... | d4cc3bacff74b26e782f0b1e666a4b13 | 955 |
= = = Microscopic characteristics = = =
| ecba0292b71d71e46a356a81eb0d47c7 | 957 |
In mass , the spores are whitish . The spores are elliptical , smooth , hyaline , devoid of oil droplets ( eguttulate ) , and have dimensions of 13 – 18 by 7 – 9 µm . They are thin walled and germinate and grow rapidly in vitro in the absence of external stimuli . The asci are 190 – 225 by 9 – 10 µm . The paraphyses a... | ebd57d98e8172a6f3301981516d2f5ad | 959 |
= = = Similar species = = =
| 655abc1b4acc929e2a0013d0919c231d | 961 |
The closely related vulcan elf cup ( Geopyxis vulcanalis ) has a pale orange to yellowish fruitbody that is deeply cup shaped before flattening in maturity , and its crushed flesh often has an odor of sulfur . It may be distinguished microscopically by its paraphyses , which lack the orange @-@ brown granules characte... | 7279636461753e5809b14451ff24ccd1 | 963 |
= = Habitat and distribution = =
| 9ea912e82694b25c90eca74c18a81efe | 965 |
Geopyxis carbonaria is widespread on burned soil or charcoal in the spring and throughout the growing season . It is one of the most common pioneer species found on burned ground . The charred litter on the forest floor increases the underlying soil pH as well as the availability of minerals . Fruitbodies are produced... | 564e9ed899c2a7facfa79f46e8c8c66d | 967 |
The fungus is found in Europe ( from where it was originally described ) , and is widespread throughout North America . The North American distribution extends north to Alaska . In 2010 , it was reported for the first time from Turkey .
| 1f90a0be13051ee0d34bb925e623f6a9 | 968 |
= = Ecology = =
| 29127b9867a90fc3cc8539652bba90cc | 970 |
Although primarily a saprotrophic fungus involved in the post @-@ fire breakdown of duff and coniferous roots , Geopyxis carbonaria has been shown to be capable of forming ectomycorrhizae with Norway spruce ( Picea abies ) . It had been demonstrated earlier in laboratory experiments that the fungus has a biotrophic in... | fe6184ca60d0b6ad278bb48f76e71ec1 | 972 |
Large fruitings of the fungus are often associated with damage to the host tree , such as that which occurs with burning . A field study conducted in Norway demonstrated that fruit bodies were more likely to be found in areas that were heavily burned , compared to locations with light to moderate burning where the tre... | 4b1e19801c949b195d2d08dc888b4478 | 973 |
= Gold dollar =
| 99cb99b8ef8dfdf508fdf65494355028 | 976 |
The gold dollar or gold one @-@ dollar piece was a coin struck as a regular issue by the United States Bureau of the Mint from 1849 to 1889 . The coin had three types over its lifetime , all designed by Mint Chief Engraver James B. Longacre . The Type 1 issue had the smallest diameter of any United States coin ever mi... | 63285cdfad4dc69a9048de104e33bb16 | 978 |
A gold dollar had been proposed several times in the 1830s and 1840s , but was not initially adopted . Congress was finally galvanized into action by the increased supply of bullion caused by the California gold rush , and in 1849 authorized a gold dollar . In its early years , silver coins were being hoarded or expor... | b6bf553412a1fc649d271e56cc7dae0f | 979 |
Gold did not again circulate in most of the nation until 1879 ; once it did , the gold dollar did not regain its place . In its final years , it was struck in small numbers , causing speculation by hoarders . It was also in demand to be mounted in jewelry . The regular issue gold dollar was last struck in 1889 ; the f... | 20a8a3136327113581d613a80d58b7f3 | 980 |
= = Background = =
| d514b18e9690308b2ac67a227be74a70 | 982 |
In proposing his plan for a mint and a coinage system , Secretary of the Treasury Alexander Hamilton in 1791 proposed that the one @-@ dollar denomination be struck both as a gold coin , and as one of silver , representative of the two metals which he proposed be made legal tender . Congress followed Hamilton 's recom... | 6409340961fcdbb0eb8f4909ce8a65d2 | 984 |
In 1831 , the first gold dollar was minted , at the private mint of Christopher Bechtler in North Carolina . Much of the gold then being produced in the United States came from the mountains of North Carolina and Georgia , and the dollars and other small gold coins issued by Bechtler circulated through that region , a... | fa1c75b5e79d96910c3f13ae7a7c1338 | 985 |
Soon after the Bechtlers began to strike their private issues , Secretary of the Treasury Levi Woodbury became an advocate of having the Mint of the United States ( " Mint " , when described as an institution ) strike the one @-@ dollar denomination in gold . He was opposed by the Mint Director , Robert M. Patterson .... | ed7106226bc7245f6590fbbabeda3164 | 986 |
Consideration was given to including the gold dollar as an authorized denomination in the revisionary legislation that became the Mint Act of 1837 . The Philadelphia newspaper Public Ledger , in December 1836 , supported a gold dollar , stating that " the dollar is the smallest gold coin that would be convenient , and... | a5e462f603c623f2e13e49e055ce3832 | 987 |
= = Inception = =
| 03834c1a7f0a7db6ced3c9309f227ac6 | 989 |
In January 1844 , North Carolina Representative James Iver McKay , the chairman of the Committee on Ways and Means , solicited the views of Director Patterson on the gold dollar . Patterson had more of Gobrecht 's pattern dollar struck to show to committee members , again advising against a coin that if issued would b... | b2952be06de0fc66e533997137a0707b | 991 |
Even before 1848 , record amounts of gold were flowing to American mints to be struck into coin , but the California Gold Rush vastly increased these quantities . This renewed calls for a gold dollar , as well as for a higher denomination than the eagle ( $ 10 piece ) , then the largest gold coin . In January 1849 , M... | a8f7a410e9022ac668092b1812eac650 | 992 |
McKay got his fellow Democrat , New Hampshire Senator Charles Atherton , to introduce the bill to authorize the gold dollar and the double eagle in the Senate on February 1 , 1849 — Atherton was chairman of the Senate Finance Committee . McKay introduced a version into the House on February 20 ; debate began the same ... | 57e1d8dd61553ff2aa76afe236594cac | 993 |
= = Preparation = =
| 17c3d495c8672cc64c566ec32008340b | 995 |
The officers at the Philadelphia Mint , including Chief Coiner Franklin Peale , were mostly the friends and relations of Director Patterson . The outsider in their midst was Chief Engraver James B. Longacre , successor to Gobrecht ( who had died in 1844 ) . A former copper @-@ plate engraver , Longacre had been appoin... | 7f99f3fdfd20a1498a4f3d2dc04c166d | 997 |
When Longacre began work on the two new coins in early 1849 , he had no one to assist him . Longacre wrote the following year that he had been warned by a Mint employee that one of the officers ( undoubtedly Peale ) planned to undermine the chief engraver 's position by having the work of preparing designs and dies do... | 96df0276f64bffdad2cbbb802e498bf4 | 998 |
The engraving was unusually minute and required very close and incessant labor for several weeks . I made the original dies and hubs for making the working dies twice over , to secure their perfect adaptation to the coining machinery . I had a wish to execute this work single handed , that I might thus silently reply ... | 8931292cc597043b54d7f4efc22e025e | 999 |
= = Original design = =
| 1c96acb11546853c16463f7936236559 | 1,001 |
The Type 1 gold dollar depicts a head of Liberty , facing left , with a coronet or tiara on her head bearing her name . Her hair is gathered in a bun ; she is surrounded by 13 stars representing the original states . The reverse features the date and denomination within a wreath , with the name of the nation near the ... | 9fc49e4bd59ee7862ebe41534687465b | 1,003 |
Contemporary reviews of the Type 1 design were generally favorable . The New York Weekly Tribune on May 19 , 1849 described the new dollar as " undoubtedly the neatest , tiniest , lightest , coin in this country ... it is too delicate and beautiful to pay out for potatoes , and sauerkraut , and salt pork . Oberon migh... | ddec67eefe2cc10527f6a23daf888fb7 | 1,004 |
= = Modifications = =
| 89e7a5fd23b900254a4c25ea49b0f595 | 1,006 |
Mint records indicate the first gold dollars were produced on May 7 , 1849 ; Longacre 's diary notes state instead that the first were struck on May 8 . A few coins in proof condition were struck on the first day , along with about 1 @,@ 000 for circulation . There are five major varieties of the 1849 gold dollar from... | d66a867380cce70ec586be5f21a58da9 | 1,008 |
The continued flow of gold from California made silver expensive in terms of gold , and U.S. silver coins began to flow out of the country for melting in 1849 , a flow that accelerated over the next several years as the price of the metal continued to rise . By 1853 , a thousand dollars in silver coin contained $ 1 @,... | 6f0c0840786ae918446a4e1953464f93 | 1,009 |
As early as 1851 , New York Congressman William Duer alleged that that Patterson had made the gold dollar too small in diameter on purpose to provoke criticism . Patterson retired that year after 16 years in his position , and under his successor , George N. Eckert , annular gold dollar and half dollar patterns were s... | d833f874a6efdcf1ecf536fc0873164a | 1,010 |
The Act of February 21 , 1853 , that had lightened the silver coins also authorized a gold three @-@ dollar piece , which began to be produced in 1854 . To ensure that the three @-@ dollar piece was not mistaken for other gold coins , it had been made thinner and wider than it would normally be , and Longacre put a di... | a9d0eb81d2ec6dacc9d5c38f5775f39c | 1,011 |
Nevertheless , the Type 2 gold dollar ( as it came to be known ) proved unsatisfactory as the mints had difficulty in striking the new coin so that all details were brought out . This was due to the high relief of the design — the three Southern branch mints especially had trouble with the piece . Many of the Type 2 p... | cd0c8156268339cd6c4a1d7c22e65685 | 1,012 |
= = = Design of Type 2 and 3 dollars = = =
| 73c040852360ef7f0cc6bb880d806780 | 1,014 |
The Type 2 and 3 gold dollars depict Liberty as a Native American princess , with a fanciful feathered headdress not resembling any worn by any Indian tribe . This image is an inexact copy of the design Longacre had made for the three @-@ dollar piece , and is one of a number of versions of Liberty Longacre created ba... | e7fc5a3370d2e391b156755326cdf263 | 1,016 |
Art historian Cornelius Vermeule deprecated the Indian princess design used by Longacre for the obverses of the Types 2 and 3 gold dollar , and for the three @-@ dollar piece , " the ' princess ' of the gold coins is a banknote engraver 's elegant version of folk art of the 1850s . The plumes or feathers are more like... | 49c19245881c82addbd971d37100d638 | 1,017 |
= = War years = =
| 39fe5c1e07af50b306aa02996afe01f7 | 1,019 |
The gold dollar continued to be produced in the late 1850s , though mintages declined from the figures of two million or more each year between 1850 and 1854 . Only about 51 @,@ 000 gold dollars were produced in 1860 , with over two @-@ thirds of that figure at Philadelphia , just under a third at San Francisco , and ... | 12a7bd7d3c280fa73029a456bf78a3ee | 1,021 |
The other candidate for the rarest from that mint is the 1861 @-@ D , with an estimated mintage of 1 @,@ 000 and perhaps 45 to 60 known . Two pairs of dies were shipped from Philadelphia to Dahlonega on December 10 , 1860 ; they arrived on January 7 , 1861 , two weeks before Georgia voted to secede from the Union , as... | a388033ea33cf3ad0f941d5a3700e7c7 | 1,022 |
Dahlonega , like the other two branch mints in the South , closed its doors after the 1861 strikings . It and the Charlotte facility never reopened ; the New Orleans Mint again struck coins from 1879 to 1909 , but did not strike gold dollars again . After 1861 , the only issuance of gold dollars outside Philadelphia w... | 11b7b607dd960d1d83e6a8acc0dfeae5 | 1,023 |
The outbreak of the Civil War shook public confidence in the Union , and citizens began hoarding specie , gold and silver coins . In late December 1861 , banks and then the federal Treasury stopped paying out gold at face value . By mid @-@ 1862 , all federal coins , even the base metal cent , had vanished from commer... | a142d289f934c8e5f555d1e066892dff | 1,024 |
= = Final years , abolition , and collecting = =
| 7fa565ca359e560b1205454f42667eeb | 1,026 |
Since gold did not circulate in the United States ( except on the West Coast ) in the postwar period , much of the production of coins of that metal in the United States was double eagles for export . Accordingly , although 1 @,@ 361 @,@ 355 gold dollars were struck in 1862 — the last time production would exceed a mi... | 1a3820b2f5b8b86540252363b23822ef | 1,028 |
In the 1870s and 1880s , public interest grew in the low @-@ mintage gold dollar . Collecting coins was becoming more popular , and a number of numismatists put aside some gold dollars and hoped for increases in value . The Mint most likely channeled its production through some favored Philadelphia dealers , though pr... | ef8f7a4404fd5d81af1da56276ff09d9 | 1,029 |
James Pollock , in his final report as Mint Director in 1873 , advocated limiting striking of gold dollars to depositors who specifically requested it . " The gold dollar is not a convenient coin , on account of its small size , and it suffers more proportionately from abrasion than larger coins . " His successors cal... | fe375020d64602ce5326ca47c63a931f | 1,030 |
A total of 19 @,@ 499 @,@ 337 gold dollars were coined , of which 18 @,@ 223 @,@ 438 were struck at Philadelphia , 1 @,@ 004 @,@ 000 at New Orleans , 109 @,@ 138 at Charlotte , 90 @,@ 232 at San Francisco and 72 @,@ 529 at Dahlonega . According to an advertisement in the February 1899 issue of The Numismatist , gold d... | 4912dba1cc1a3e8237107b21bf2725e7 | 1,031 |
= = Commemorative gold dollars = =
| c5b3547dd92630633fe36c2ed92cb485 | 1,033 |
The gold dollar had a brief resurrection during the period of Early United States commemorative coins . Between 1903 and 1922 nine different issues were produced , with a total mintage of 99 @,@ 799 . These were minted for various public events , did not circulate , and none used Longacre 's design .
| 77b9871332c1f5bdc1d42251d8a82f34 | 1,035 |
= Johnson – Corey – Chaykovsky reaction =
| e03bd2b73b644afb2c909bc4d1733783 | 1,038 |
The Johnson – Corey – Chaykovsky reaction ( sometimes referred to as the Corey – Chaykovsky reaction or CCR ) is a chemical reaction used in organic chemistry for the synthesis of epoxides , aziridines , and cyclopropanes . It was discovered in 1961 by A. William Johnson and developed significantly by E. J. Corey and ... | 375b67086d1b679cfe6caa08a2d3376b | 1,040 |
The reaction is most often employed for epoxidation via methylene transfer , and to this end has been used in several notable total syntheses ( See Synthesis of epoxides below ) . Additionally detailed below are the history , mechanism , scope , and enantioselective variants of the reaction . Several reviews have been... | 8259c5f5c7ec76e169a0e4c823e0a9dc | 1,041 |
= = History = =
| fd3fc667e330e6e3944a4f085f9ef39d | 1,043 |
The original publication by Johnson concerned the reaction of 9 @-@ dimethylsulfonium fluorenylide with substituted benzaldehyde derivatives . The attempted Wittig @-@ like reaction failed and a benzalfluorene oxide was obtained instead , noting that " Reaction between the sulfur ylid and benzaldehydes did not afford ... | be69b9dc1aaff61ffc312ee77b90139d | 1,045 |
The subsequent development of ( dimethyloxosulfaniumyl ) methanide , ( CH3 ) 2SOCH2 and ( dimethylsulfaniumyl ) methanide , ( CH3 ) 2SCH2 ( known as Corey – Chaykovsky reagents ) by Corey and Chaykovsky as efficient methylene @-@ transfer reagents established the reaction as a part of the organic canon .
| a6b87491c8a052614e9065971699513a | 1,046 |
= = Mechanism = =
| f50fd04c98be648a8afb166be44f9525 | 1,048 |
The reaction mechanism for the Johnson – Corey – Chaykovsky reaction consists of nucleophilic addition of the ylide to the carbonyl or imine group . A negative charge is transferred to the heteroatom and because the sulfonium cation is a good leaving group it gets expelled forming the ring . In the related Wittig reac... | 7d20eb90d0f7b668880b15338f8b33b2 | 1,050 |
The trans diastereoselectivity observed results from the reversibility of the initial addition , allowing equilibration to the favored anti betaine over the syn betaine . Initial addition of the ylide results in a betaine with adjacent charges ; density functional theory calculations have shown that the rate @-@ limit... | 29e9c3d0c2119130e5f1c06f4fde4c6f | 1,051 |
The degree of reversibility in the initial step ( and therefore the diastereoselectivity ) depends on four factors , with greater reversibility corresponding to higher selectivity :
| 8cb6c3e5aa6cc13a8fd761669d9ea760 | 1,052 |
Stability of the substrate with higher stability leading to greater reversibility by favoring the starting material over the betaine .
| ff3c59da05f53a0bb947cc5521c6f528 | 1,053 |
Stability of the ylide with higher stability similarly leading to greater reversibility .
| ce87e4ed234c66a3b3af3086c7952818 | 1,054 |
Steric hindrance in the betaine with greater hindrance leading to greater reversibility by disfavoring formation of the intermediate and slowing the rate @-@ limiting rotation of the central bond .
| e5c127f31748a1c791f290fc03bb129b | 1,055 |
Solvation of charges in the betaine by counterions such as lithium with greater solvation allowing more facile rotation in the betaine intermediate , lowering the amount of reversibility .
| 19a486e4625590010c2b0d97db9cf7c5 | 1,056 |
= = Scope = =
| 0343a1b44cc342b78dd0950895e277f3 | 1,058 |
The application of the Johnson – Corey – Chaykovsky reaction in organic synthesis is diverse . The reaction has come to encompass reactions of many types of sulfur ylides with electrophiles well beyond the original publications . It has seen use in a number of high @-@ profile total syntheses , as detailed below , and... | b33249c7fa7f8a6f12a43d7d34609d8b | 1,060 |
= = = Types of ylides = = =
| 17f233fa37ef11b00ff82840786e4237 | 1,062 |
Many types of ylides can be prepared with various functional groups both on the anionic carbon center and on the sulfur . The substitution pattern can influence the ease of preparation for the reagents ( typically from the sulfonium halide , e.g. trimethylsulfonium iodide ) and overall reaction rate in various ways . ... | 855e0c2f11bdc57d5881a3083a9d253a | 1,064 |
Use of a sulfoxonium allows more facile preparation of the reagent using weaker bases as compared to sulfonium ylides . ( The difference being that a sulfoxonium contains a doubly bonded oxygen whereas the sulfonium does not . ) The former react slower due to their increased stability . In addition , the dialkylsulfox... | ff1e0f32751d87208f7584d19ee18f83 | 1,065 |
The vast majority of reagents are monosubstituted at the ylide carbon ( either R1 or R2 as hydrogen ) . Disubstituted reagents are much rarer but have been described :
| 815f78c1bf8790daf3ee9c4669b005a3 | 1,066 |
If the ylide carbon is substituted with an electron @-@ withdrawing group ( EWG ) , the reagent is referred to as a stabilized ylide . These , similarly to sulfoxonium reagents , react much slower and are typically easier to prepare . These are limited in their usefulness as the reaction can become prohibitively slugg... | 91ea7e91b443b8477f5023ff57e47708 | 1,067 |
If the ylide carbon is substituted with an aryl or allyl group , the reagent is referred to as a semi @-@ stabilized ylide . These have been developed extensively , second only to the classical methylene reagents ( R1 = R2 = H ) . The substitution pattern on aryl reagents can heavily influence the selectivity of the r... | 46ed754081278b04cab4f9b33335cb2f | 1,068 |
If the ylide carbon is substituted with an alkyl group the reagent is referred to as an unstabilized ylide . The size of the alkyl groups are the major factors in selectivity with these reagents .
| 47d1e7a8d7f95c9f79e350508d0122ae | 1,069 |
The R @-@ groups on the sulfur , though typically methyls , have been used to synthesize reagents that can perform enantioselective variants of the reaction ( See Variations below ) . The size of the groups can also influence diastereoselectivity in alicyclic substrates .
| 9214fe2f30444280cffde3ce59d415a5 | 1,070 |
= = = Synthesis of epoxides = = =
| cace5757ecf8cdc31a03e7b70db4b1be | 1,072 |
Reactions of sulfur ylides with ketones and aldehydes to form epoxides are by far the most common application of the Johnson – Corey – Chaykovsky reaction . Examples involving complex substrates and ' exotic ' ylides have been reported , as shown below .
| 0d32dcacbae1b667bd09d1739e0144f5 | 1,074 |
The reaction has been used in a number of notable total syntheses including the Danishefsky Taxol total synthesis , which produces the chemotherapeutic drug taxol , and the Kuehne Strychnine total synthesis which produces the pesticide strychnine .
| 96316a99a2d65791bd0955bcfeccc495 | 1,075 |
= = = Synthesis of aziridines = = =
| d46a23da7df7892f023168f32dfe6684 | 1,077 |
The synthesis of aziridines from imines is another important application of the Johnson – Corey – Chaykovsky reaction and provides an alternative to amine transfer from oxaziridines . Though less widely applied , the reaction has a similar substrate scope and functional group tolerance to the carbonyl equivalent . The... | 9da27a968a3b2a09f54d454a1d0b6365 | 1,079 |
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