Academic literature on the topic 'Alkyne protecting groups'

D. Srinivasa Reddy of the National Chemical Laboratory converted (Org. Lett. 2015, 17, 2090) the selenide 1 to the alkene 2 under ozonolysis conditions. Takamitsu Hosoya of the Tokyo Medical and Dental University found (Chem. Commun. 2015, 51, 8745) that even highly strained alkynes such as 4 can be generated from a sulfinyl vinyl triflate 3. An alkyne can be protected as the dicobalt hexacarbonyl complex. Joe B. Gilroy and Mark S. Workentin of the University of Western Ontario found (Chem. Commun. 2015, 51, 6647) that following click chemistry on a non-protected distal alkyne, deprotection of 5 to 6 could be effected by exposure to TMNO. Stefan Bräse of the Karlsruhe Institute of Technology and Irina A. Balova of Saint Petersburg State University showed (J. Org. Chem. 2015, 80, 5546) that the bend of the Co complex of 7 enabled ring-closing metathesis, leading after deprotection to 8. Morten Meldal of the University of Copenhagen devised (Eur. J. Org. Chem. 2015, 1433) 9, the base-labile protected form of the aldehyde 10. Nicholas Gathergood of Dublin City University and Stephen J. Connon of the University of Dublin developed (Eur. J. Org. Chem. 2015, 188) an imidazolium catalyst for the exchange deprotection of 11 to 13, with the inexpensive aldehyde 12 as the acceptor. Peter J. Lindsay-Scott of Eli Lilly demonstrated (Org. Lett. 2015, 17, 476) that on exposure to KF, the isoxa­zole 14 unraveled to the nitrile 15. Masato Kitamura of Nagoya University observed (Tetrahedron 2015, 71, 6559) that the allyl ester of 16 could be removed to give 17, with the other alkene not affected. Benzyl ethers are among the most common of alcohol protecting groups. Yongxiang Liu and Maosheng Cheng of Shenyang Pharmaceutical University showed (Adv. Synth. Catal. 2015, 357, 1029) that 18 could be converted to 19 simply by expo­sure to benzyl alcohol in the presence of a gold catalyst. Reko Leino of Åbo Akademi University developed (Synthesis 2015, 47, 1749) an iron catalyst for the reductive benzylation of 20 to 21. Related results (not illustrated) were reported (Org. Lett. 2015, 17, 1778) by Chae S. Yi of Marquette University.

Cancheng Guo of Hunan University devised (J. Org. Chem. 2014, 79, 2709) con­ditions for the oxidative cleavage of an alkyne 1 to the esters 2 and 3. Hirokazu Arimoto of Tohoku University found (Chem. Commun. 2014, 50, 2758) that IBX oxidized a primary alcohol 4 to the acid 5 one carbon shorter. David Milstein of the Weizmann Institute of Science uncovered (J. Am. Chem. Soc. 2014, 136, 2998) condi­tions for the direct oxidation of the cyclic amine 6 to the lactam 7, with concomitant evolution of H₂. Cyclic ene sulfonamides such as 9 are versatile synthetic intermediates. Henri Doucet of the Université de Rennes reported (Adv. Synth. Catal. 2014, 356, 119) the regioselective conversion of 8 to 9. In this case, the oxidizing agent was the organo-PdBr intermediate. There have been many reports of the functionalization of the oxygenated carbons of cyclic ethers, as exemplified by the conversion of 10 to 11, observed (J. Org. Chem. 2014, 79, 3847) by Jianlin Han of Nanjing University. If these methods were regiose­lective with an acyclic benzyl ether, this could be a new method for the removal of that common protecting group. Jianliang Xiao of the University of Liverpool described (J. Am. Chem. Soc. 2014, 136, 8350) a selective benzylic ether oxidation that converted 12 to 13. Baris Temelli of Hacettepe University effected (Synthesis 2014, 46, 1407) the conversion of a primary nitro compound 14 into the corresponding nitrile 15. Jean- Michel Vatèle of Université Lyon 1 oxidized (Synlett 2014, 25, 1275) the primary alcohol 16 to the nitrile 17. Many methods have been put forward for the oxidation of primary alcohols to alde­hydes and secondary alcohols to ketones. Piperidinium oxy radicals such as TEMPO are widely used to catalyze this transformation. Yoshikazu Kimura of Iharanikkei Chemical Industry Co. Ltd. established (Synlett 2014, 25, 596) a manufacturing proc­ess for crystalline NaOCl•5H₂O that served as the bulk oxidant for the conversion of 18 to 19. Neither a ketone nor an aldehyde was chlorinated under the reaction condi­tions. Yoshiharu Iwabuchi of Tohoku University showed (Angew. Chem. Int. Ed. 2014, 53, 3236) that with his piperidinium oxy radical AZADO and Cu catalysis, air could be the bulk oxidant for the otherwise difficult conversion of the amino alcohol 20 to the amino ketone 21.

Craig M. Williams of the University of Queensland and John Tsanaktsidis of CSIRO Victoria decarboxylated (Org. Lett. 2011, 13, 1944) the acid 1 to the hydrocarbon 2 by coupling the crude acid chloride, formed in CHCl3, with 3 while irradiating with a tungsten bulb. In a related development, David C. Harrowven of the University of Southampton showed (Chem. Commun. 2011, 46, 6335, not illustrated) that tin residues can be removed from a reaction mixture by passage through silica gel containing 10% K2CO3. Sangho Koo of Myong Ji University selectively removed (Org. Lett. 2011, 13, 2682) the allylic oxygen of 5, leaving the other protected alcohol. Donald Poirier of Laval University reduced (Synlett 2011, 2025) the nitrile of 7 to a methyl group. Kiyotomi Kaneda of Osaka University prepared (Chem. Eur. J. 2010, 16, 11818; Angew. Chem. Int. Ed. 2011, 50, 2986) supported Au nanoparticles that deoxygenated an epoxide 9 to the alkene 10. Epoxides of cyclic alkenes also worked well. Shahrokh Saba of Fordham University aminated (Tetrahedron Lett. 2011, 52, 129) the ketone 11 by heating it with an amine 12 in the presence of ammonium formate. Shuangfeng Yin and Li-Biao Han of Hunan University devised (J. Am. Chem. Soc. 2011, 133, 17037) catalyst systems that reduced the alkyne 14 selectively to either the Z or the E product. Professor Kaneda uncovered (Chem. Lett. 2011, 40, 405) a reliable Pd catalyst for the hydrogenation (not illustrated) of an alkyne to the Z alkene. David R. Spring of the University of Cambridge established (Synlett 2011, 1917) biphasic reaction conditions for the conversion of 16 to the azide 18 that were compatible with the base-sensitive Fmoc protecting group. Noritaka Mizuno of the University of Tokyo developed (J. Org. Chem. 2011, 76, 4606) a Ru catalyst for the transformation of an alkyl azide 19 to the nitrile 20. Chi-Ming Che of the University of Hong Kong (Synlett 2011, 1174) and Philip Wai Hong Chan of Nanyang Technological University (J. Org. Chem. 2011, 76, 4894) independently oxidized an aldehyde 21 to the amide 22.

The Z alkene of nakadomarin A 3 suggested to Raymond L. Funk an approach (Org. Lett. 2010, 12, 4912) based on ring-closing alkyne metathesis. The efficient assembly of 3 he reported illustrates the power of convergent design in target-directed synthesis. A practical limit on applications of alkyne metathesis is the requirement for internal alkynes, necessitating methyl capping of a terminal alkyne. In an alternative approach, Professor Funk took advantage of the long-known ( J. Chem. Soc. 1954 , 3201) equilibration of a terminal alkyne 4 to the internal alkyne 5. Homologation of 5 with the phosphonate 6, followed by condensation with the ketone 7, then delivered the furan 8. The assembly of the other half of 1 began with the commercial alcohol derived by reduction of D -pyroglutamic acid. Protection gave 9, which on hydride addition and dehydration was converted to 10. One-carbon homologation with the Vilsmeier-Haack reagent proceeded with the expected regiocontrol. This set the stage for the triply convergent assembly of 14 , first reductive amination of the aldehyde 11 with 12 , then acylation of the resulting secondary amine with 13. The nucleophilic 14 was condensed with the aldehyde 8 to give an enone (not illustrated). Exposure of the enone to InCl 3 initiated an elegant cascade cyclization, first of the enamide in a conjugate sense to the enone, then Friedel-Crafts addition of the resulting N-stabilized carbocation to the furan, to deliver 15. The pendant silyloxymethyl group exerted the hoped-for diastereocontrol, allowing the direct construction of the central tetracycle of 3. Hydrolysis and decarboxylation completed the assembly of the diyne 1. Initially, it was found that exposure of 1 to a molybdenum catalyst delivered 2 in only modest yield. As an alternative, they employed the technically more challenging tungsten-based Schrock catalyst. Later, they found that the recently developed Fürstner Mo protocol also worked well. The amide 2 could readily be carried on to the triene 18. With the first-generation Grubbs catalyst G1, kinetic ring-closing metathesis of 18, to complete the assembly of (-)-nakadomarin 3, could be effected without jeopardizing the existing Z alkene.

The effects of R 68 070, an oxime-alkane carboxylic acid derivative combining specific thromboxane A2 (TXA2) synthetase inhibition with TXA2/prostaglandin endoperoxide receptor blockade in one molecule, were investigated in a model of photochemically induced stroke in spontaneously hypertensive rats.Each experimental group was compared with an untreated control group. All animals were anesthetized with halothane in N20/02 and artificially ventilated. After incision of the scalp and stereotaxic positioning of a fibre optic light source, halothane was discontinued. When physiological variables r

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