Reduction and Oxidation

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Protecting Group ◽  
Methyl Group ◽  
Ru Catalyst ◽  
University Of Cambridge ◽  
Related Development ◽  
Biphasic Reaction ◽  
Catalyst Systems ◽  
Fmoc Protecting Group ◽  
The University ◽  
Technological University

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.

Functionalization and Homologation of C-H Bonds

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Crop Protection ◽  
Oxidative Cyclization ◽  
South Florida ◽  
State University ◽  
Ru Catalyst ◽  
University Of Oklahoma ◽  
Princeton University ◽  
La Jolla ◽  
The University ◽  
Technological University

Justin Du Bois of Stanford University developed (J. Am. Chem. Soc. 2010, 132, 10202) a Ru catalyst for the stereoretentive hydroxylation of 1 to 2. John T. Groves of Princeton University effected (J. Am. Chem. Soc. 2010, 132, 12847) equatorial chlorination of the test substrate 3. Kenneth M. Nicholas of the University of Oklahoma found (J. Org. Chem. 2010, 75, 7644) that I2 catalyzed the amination of 5. Thorsten Bach of the Technische Universität München established (Org. Lett. 2010, 12, 3690) that the amination of 7 proceeded with significant diastereoselectivity. Phil S. Baran of Scripps/La Jolla compiled (Synlett 2010, 1733) an overview of the development of C-H oxidation. Tethering can improve the selectivity of C-H functionalization. X. Peter Zhang of the University of South Florida devised (Angew. Chem. Int. Ed. 2010, 49, 10192) a Co catalyst for the cyclization of 9 to 10. Teck-Peng Loh of Nanyang Technological University established (Angew. Chem. Int. Ed. 2010, 49, 8417) conditions for the oxidation of 11 to 12. Jin-Quan Yu, also of Scripps/La Jolla, effected (J. Am. Chem. Soc. 2010, 132, 17378) carbonylation of methyl C-H of 13 to give 14. Sunggak Kim, now also at Nanyang Technological University, established (Synlett 2010, 1647) conditions for the free-radical homologation of 15 to 17. Gong Chen of Pennsylvania State University extended (Org. Lett. 2010, 12, 3414) his work on remote Pd-mediated activation by cyclizing 18 to 19. Many schemes have been developed in recent years for the oxidation of substrates to reactive electrophiles. Gonghua Song of the East China University of Science and Technology and Chao-Jun Li of McGill University reported (Synlett 2010, 2002) Fe nanoparticles for the oxidative coupling of 20 with 21. Zhi-Zhen Huang of Nanjing University found (Org. Lett. 2010, 12, 5214) that protonated pyrrolidine 25 was important for mediating the site-selective coupling of 24 with 23. Y. Venkateswarlu of the Indian Institute of Chemical Technology, Hyderabad, was even able (Tetrahedron Lett. 2010, 51, 4898) to effect coupling with a cyclic alkene 28. AB3217-A 32, isolated in 1992, was shown to have marked activity against two spotted spider mites. Christopher R. A. Godfrey of Syngenta Crop Protection, Münchwilen, prepared (Synlett 2010, 2721) 32 from commercial anisomycin 30a. The key step in the synthesis was the oxidative cyclization of 30b to 31.

Preparation of Heterocycles: The Boukouvalas Synthesis of (−)-Auxofuran

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Triethyl Phosphite ◽  
Florida State University ◽  
State University ◽  
University Of Iowa ◽  
Michael Adduct ◽  
Related Development ◽  
The University ◽  
Technological University ◽  
École Polytechnique ◽  
Simon Fraser University

Nabyl Merbouh and Robert Britton of Simon Fraser University developed (Eur. J. Org. Chem. 2013, 3219) a general route to a 2,5-disubstituted furan 3 by taking advantage of the ready α-chlorination of an aldehyde 1, followed by coupling with a ketone eno­late 2. Jérôme Waser of the Ecole Polytechnique Fédérale de Lausanne used (Angew. Chem. Int. Ed. 2013, 52, 6743) 5 to oxidize the allene 4 to the furan 6. Qian Zhang and Xihe Bi of Northeast Normal University used (Angew. Chem. Int. Ed. 2013, 52, 6953) Ag catalysis to prepare the pyrrole 9 by coupling the alkyne 7 with the isonitrile 8. Aiwen Lei of Wuhan University reported (Angew. Chem. Int. Ed. 2013, 52, 6958) similar results. Professor Lei also developed (Chem. Commun. 2013, 49, 5853) the Pd-catalyzed oxidation of the allyl imine 10 to the pyrrole 11. Kamal K. Kapoor of the University of Jammu reduced (Tetrahedron Lett. 2013, 54, 5699) the Michael adduct 12 to the pyrrole 13 with triethyl phosphite. Edgar Haak of the Otto-von-Guericke-Universität, Magdeburg condensed (Eur. J. Org. Chem. 2013, 7354) the alkynyl carbinol 14 with aniline to give the N-phenyl pyrrole 15. Jean Rodriguez and Thierry Constantieux of Aix-Marseille Université prepared (Eur. J. Org. Chem. 2013, 4131) the pyridine 18 by combining the ketone 16 and the unsaturated aldehyde 17 with NH4OAc. Teck-Peng Loh of the University of Sciences and Technology of China and Nanyang Technological University found (Angew. Chem. Int. Ed. 2013, 52, 8584) that TMEDA was an effective organocatalyst for the assembly of the pyridine 21 from 19 and 20. Andrew D. Smith of the University of St Andrews showed (Angew. Chem. Int. Ed. 2013, 52, 11642) that the pyridyl tosylate 24, avail­able by the combination of 22 and 23, readily coupled with both carbon and amine nucleophiles. In a related development, D. Tyler McQuade of Florida State University prepared (Org. Lett. 2013, 15, 5298) the 2-bromopyridine 26 from the alkylidene malononitrile 25. Two versatile approaches to substituted indoles were recently described. David F. Wiemer of the University of Iowa cyclized (J. Org. Chem. 2013, 78, 9291) the Stobbe product 27 to the 3-bromo indole 28.

Functional Group Protection

2015 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
National Laboratory ◽  
Primary Alcohol ◽  
Selective Reduction ◽  
State University ◽  
Protecting Group ◽  
Los Alamos National Laboratory ◽  
Ru Catalyst ◽  
New Mexico State University ◽  
Peking University ◽  
The University

Zhong-Jun Li of Peking University developed (J. Org. Chem. 2011, 76, 9531) a Co catalyst for selectively replacing one benzyl protecting group of 1 with silyl. Carlo Unverzagt of Universität Bayreuth devised (Chem. Commun. 2011, 47, 10485) oxidative conditions for debenzylating the azide 3 to 4. Tadashi Katoh of Tohoku Pharmaceutical University found (Tetrahedron Lett. 2011, 52, 5395) that the dimethoxybenzyl protecting group of 5 could be selectively removed in the presence of benzyl and p-methoxybenzyl. Scott T. Phillips of Pennsylvania State University showed (J. Org. Chem. 2011, 76, 7352) that in the presence of phosphate buffer, catalytic fluoride was sufficient to desilylate 7. Philip L. Fuchs of Purdue University employed (J. Org. Chem. 2011, 76, 7834, not illustrated) the neutral Robins conditions (Tetrahedron Lett. 1992, 33, 1177) to effect a critical desilylation. Pengfei Wang of the University of Alabama at Birmingham found (J. Org. Chem. 2011, 76, 8955) that an excess of the diol 9 both oxidized the primary alcohol 10 and installed the photolabile protecting group on the product aldehyde. Hiromichi Fujioka of Osaka University showed (Angew. Chem. Int. Ed. 2011, 50, 12232) that addition of Ph3P to 12 transiently protected the aldehyde, allowing selective reduction of the ketone to the alcohol. Willi Bannwarth of Albert-Ludwigs-Universität Freiburg deprotected (Angew. Chem. Int. Ed. 2011, 50, 6175) the chelating amide of 14, leaving the usually sensitive Fmoc group in place. Bruce C. Gibb, now at Tulane University, hydrolyzed (Nature Chem. 2010, 2, 847) 16 more rapidly than the very similar 17, by selective equilibrating complexation of 16 and 17 with a cavitand. Aravamudan S. Gopalan of New Mexico State University converted (Tetrahedron Lett. 2010, 51, 6737) proline 19 to the amide ester 10 by exposure to triethyl orthoacetate. K. Rajender Reddy of the Indian Institute of Chemical Technology oxidized (Angew. Chem. Int. Ed. 2011, 50, 11748) the formamide 22 to the carbamate 23 by exposure to H2O2 in the presence of 21. James M. Boncella of the Los Alamos National Laboratory deprotected (Org. Lett. 2011, 13, 6156) 24 by exposure to visible light in the presence of a Ru catalyst.

C–H Functionalization: The Maimone Synthesis of Podophyllotoxin

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
University Of California ◽  
University Of Illinois ◽  
Methyl Group ◽  
Du Bois ◽  
Princeton University ◽  
University Of Cambridge ◽  
Rh Catalyst ◽  
Institute Of Technology ◽  
La Jolla ◽  
The University

Matthias Beller of the Universität Rostock developed (Angew. Chem. Int. Ed. 2014, 53, 6477) a Rh catalyst for the acceptorless dehydrogenation of an alkane 1 to the alkene 2. Bhisma K. Patel of the Indian Institute of Technology Guwahati effected (Org. Lett. 2014, 16, 3086) oxidation of cyclohexane 3 and 4 to form the allylic benzoate 5. Justin Du Bois of Stanford University devised (Chem. Sci. 2014, 5, 656) an organocatalyst that mediated the hydroxylation of 6 to 7. Vladimir Gevorgyan of the University of Illinois, Chicago hydrosilylated (Nature Chem. 2014, 6, 122) 8 to give an intermediate that, after Ir-catalyzed intramolecular C–H functionalization followed by oxidation, was converted to the diacetate 9. Sukbok Chang of KAIST used (J. Am. Chem. Soc. 2014, 136, 4141) the methoxime of 10 to direct selective amination of the adjacent methyl group, leading to 11. John F. Hartwig of the University of California, Berkeley effected (J. Am. Chem. Soc. 2014, 136, 2555) diastereoselective Cu-catalyzed amination of 12 with 13 to make 14. David W. C. MacMillan of Princeton University accomplished (J. Am. Chem. Soc. 2014, 136, 6858) β-alkylation of the aldehyde 15 with acrylonitrile 16 to give 17. Yunyang Wei of the Nanjing University of Science and Technology alkenylated (Chem. Sci. 2014, 5, 2379) cyclohexane 3 with the styrene 18, leading to 19. Bin Wu of the Kunming Institute of Botany described (Org. Lett. 2014, 16, 480) the Pd-mediated cyclization of 20 to 21. Similar results using Cu catalysis were reported (Angew. Chem. Int. Ed. 2014, 53, 3496, 3706) by Yoichiro Kuninobu and Motomu Kanai of the University of Tokyo and by Haibo Ge of IUPUI. Jin-Quan Yu of Scripps La Jolla constructed (J. Am. Chem. Soc. 2014, 136, 5267) the lactam 24 by γ-alkenyl­ation of the amide 22 with 23, followed by cyclization. Philippe Dauban of CNRS Gif-sur-Yvette prepared (Eur. J. Org. Chem. 2014, 66) the useful crystalline chiron 27 by asymmetric amination of the enol triflate 26 with 25. Matthew J. Gaunt of the University of Cambridge showed (J. Am. Chem. Soc. 2014, 136, 8851) that the phenylative cyclization of 28 with 29 to 30 proceeded with near-perfect retention of absolute configuration.

Advances in Organic Functional Group Transformation

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Carboxylic Acids ◽  
Allyl Ether ◽  
Primary Alcohols ◽  
Ru Catalyst ◽  
University Of Technology ◽  
National University ◽  
Tokyo Institute ◽  
Institute Of Technology ◽  
The University ◽  
Technological University

There have been several significant advances in N-alkylation using alcohols. Matthias Beller of Universität Rostock devised (Angew. Chem. Int. Ed. 2010, 49, 8126) a Ru catalyst for the amination of secondary and benzylic primary alcohols with ammonia. Dieter Vogt of the Eindhoven University of Technology reported (Angew. Chem. Int. Ed. 2010, 49, 8130) related transformations. Pei-Qiang Huang of Xiamen University showed (Chem. Commun. 2010, 46, 7834) that debenzylation of 3 in methanol led to the N-methyl amine 4. Parallel results have been reported with Ir (J. Am. Chem. Soc. 2010, 132, 15108), Au (Chem. Eur. J. 2010, 16, 13965), and Cu (Chem. Lett. 2010, 39, 1182). Peter J. Scammells of Monash University found (J. Org. Chem. 2010, 75, 4806) that demethylation of an N-oxide could be effected with Fe powder. Yao Fu and Qingxiang Guo of the University of Science and Technology of China N-vinylated (Tet. Lett. 2010, 51, 5476) a sulfonamide 7 with vinyl acetate and a Pd catalyst. Acyl amides could also be N-vinylated under these conditions. Hirokazu Urabe of the Tokyo Institute of Technology reported (Org. Lett. 2010, 12, 4137) that the stereodefined secondary sulfonamide of 9 could be displaced by an internal nucleophile, to give the product 11 with inversion of absolute configuration. Teruo Umemoto of IM&T Research devised (J. Am. Chem. Soc. 2010, 132, 18199) the remarkable fluorinating agent 13. In addition to converting secondary alcohols to the corresponding fluorides and ketones to gem-difluorides, 13 cleanly converted the carboxylic acids of 12 to trifluoromethyl groups. Paul G. Williard of Brown University demonstrated (Org. Lett. 2010, 12, 5378) that LDA converted an allyl ether 15 specifically to the (Z)-propenyl ether 16. Phil Lee Ho of Kangwon National University and Sunggak Kim of Nanyang Technological University could add (Angew. Chem. Int. Ed. 2010, 49, 6806) a phosphate to an alkyne 17 to make either the less substituted or the more substituted enol phosphate. Professor Kim reported (J. Org. Chem. 2010, 75, 7928) similar results with the addition of carboxylic acids.

Selective Functionalization of C–H Bonds

2017 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
University Of Illinois ◽  
Ru Catalyst ◽  
Princeton University ◽  
Selective Functionalization ◽  
Terminal Alkene ◽  
Osaka Prefecture ◽  
Indian Institute Of Science ◽  
The University ◽  
Technological University ◽  
Catalyzed Oxidation

Jianhui Huang and Kang Zhao of Tianjin University devised (Chem. Commun. 2013, 49, 1211) a protocol for the oxidation of a terminal alkene 1 to the valuable four-carbon synthon 2. M. Christina White of the University of Illinois effected (J. Am. Chem. Soc. 2013, 135, 7831) the oxidation of the terminal alkene 3 to the enone 4. Miquel Costas of the Universitat de Girona developed (J. Org. Chem. 2013, 78, 1421; Chem. Eur. J. 2013, 19, 1908) a family of Fe catalysts for the oxidation of methylenes to ketones. Depending on the catalyst, any of the three ketones from the oxidation of 5, including 6, could be made the dominant product. Yumei Xiao and Zhaohai Qin of China Agricultural University optimized (Synthesis 2013, 45, 615) the Co-catalyzed oxidation of the methyl group of 7 to give the aldehyde 8. Thanh Binh Nguyen of CNRS Gif-sur-Yvette established (J. Am. Chem. Soc. 2013, 135, 118) a protocol (not illustrated) for the oxidation of methyl groups on heteroaromatics. Shunsuke Chiba of Nanyang Technological University cyclized (Org. Lett. 2013, 15, 212, 3214) the amidine 9 to 10, and the hydrazone 11 to 12. These cyclizations proceeded by sequential C–H abstraction followed by recombination, and so were racemizing. In contrast, the conversion of 13 to 14, developed (Science 2013, 340, 591) by Theodore A. Betley of Harvard University, proceeded with substantial reten­tion of absolute configuration. Tsutomu Katsuki of Kyushu University designed (Angew. Chem. Int. Ed. 2013, 52, 1739) a Ru catalyst that was selective for the allylic position of the E-alkene 15 to give 16. Amination was highly regioselective, and proceeded with excellent ee. Ilhyong Ryu of Osaka Prefecture University and Maurizio Fagnoni of the University of Pavia reported (Org. Lett. 2013, 15, 2554) the direct carbonylation of 17 to the amide 18. David W. C. MacMillan of Princeton University devised (Science 2013, 339, 1593) a protocol for the β- arylation of an aldehyde 19 to give 20. Directed palladation of distal C–H bonds continues to be developed. Srinivasarao Arulananda Babu of the Indian Institute of Science Education and Research effected (Org. Lett. 2013, 15, 3238) diastereoselective arylation of the cyclopropane 21 with 22 to give 23.

Functional Group Protection: The Kraus Synthesis of Bauhinoxepin J

2013 ◽  
Author(s):  
Douglass F. Taber
Keyword(s):  
Indian Institute ◽  
University Of Pennsylvania ◽  
Protecting Group ◽  
Keto Esters ◽  
Mild Conditions ◽  
National University ◽  
The University ◽  
Technological University ◽  
Convenient Preparation ◽  
Robust Protocol

Amos B. Smith III of the University of Pennsylvania found (Synlett 2009, 3131) that the advanced SAMP intermediate 1 could be deprotected to 2 without racemization under mild oxidative conditions. Akihiko Ouchi of the National Institute of Advanced Industrial Science and Technology, Tsukuba, showed (Organic Lett. 2009, 11, 4870) that the C-Te of 3 was easily oxidized to the aldehyde 4. Secondary C-Te bonds were converted to ketones. Asit K. Chakraborti of NIPER prepared (J. Org. Chem. 2009, 74, 5967) esters by warming an acid 5 with an alcohol 6 in the presence of acidic silica gel. Gilles Quéléver of Aix-Marseille Université established (Tetrahedron Lett. 2009, 50, 4346) that a cyanomethyl ester 8, readily prepared from the acid, efficiently exchanged with an alcohol 9 to give the ester 10. Martin J. Lear of the National University of Singapore protected (Tetrahedron Lett. 2009, 50, 5267) an alcohol 11 as the p -methoxybenzyl ether 13 under mild conditions (AgOTf/DTBMP) with the new reagent 12 . Isao Kadota of Okayama University selectively removed (Tetrahedron Lett. 2009, 50, 4552) the primary PMB ether from 14 to give 15. Hiromishi Fujioka of Osaka University, starting (Organic Lett. 2009, 11, 5138) from 16, was able to selectively prepare either the primary protected 18 or the secondary protected 19. In other developments (not pictured), Mattie S. M. Timmer and Brendan A. Burkett of Victoria University of Wellington devised (Tetrahedron Lett. 2009, 50, 7199) a convenient preparation for azulene-containing α-keto esters. The distinctively colored protecting group was conveniently removed in the presence of other esters by treatment with o-phenylenediamine. Scott D. Taylor of the University of Waterloo established (J. Org. Chem. 2009, 74, 9406) a robust protocol for converting alcohols to the corresponding protected sulfates. P. Shanthan Rao of the Indian Institute of Chemical Technology, Hyderabad, showed (Tetrahedron Lett. 2009, 50, 7099) that an amine 20 was formylated by warming with formic acid in the presence of ZnCl2. The easily hydrolyzed formamide 21 is readily converted to the corresponding isonitrile. Shiyue Fang of Michigan Technological University selectively monoacylated (Tetrahedron Lett. 2009, 50, 5741) the symmetrical diamine 22 using phenyl esters.

Organocatalytic Ring Construction: The Corey Synthesis of Coraxeniolide A

2011 ◽  
Author(s):  
Douglass Taber
Keyword(s):  
Michael Addition ◽  
State University ◽  
Henry Reaction ◽  
Max Planck ◽  
Keto Ester ◽  
Colorado State University ◽  
University Of Cambridge ◽  
Diastereomeric Mixture ◽  
The University ◽  
Technological University

Armando Córdova of Stockholm University has found (Tetrahedron Lett. 2008, 49, 4209) that the organocatalyst 3a effected enantioselective conjugate addition of bromonitromethane 2 to the α,β-unsaturated aldehyde 1, to give the cyclopropane 4 as a ~ 1:1 diastereomeric mixture, both in high ee. Tomislav Rovis of Colorado State University has published (J. Org. Chem. 2008, 73, 2033) a detailed account of his development of catalysts such as 6, that effected enantioselective cyclization of 5 to 7 with excellent ee. Karl Anker Jørgensen of Aarhus University has employed (J. Am. Chem. Soc. 2008, 130, 4897) chiral quaternary salts derived from quinine that mediated the enantioselective addition of prochiral rings such as 8 to the allenoate ester 9 to give 10 with high ee. Organocatalysts have also been used to prepare more highly substituted cyclohexane derivatives. Guofu Zhong of Nanyang Technological University used (Organic Lett. 2008, 10, 2437) a quinine-derived secondary amine to catalyze the Michael addition of 12 to 11 followed by intramolecular aldol (Henry) reaction, to give 13. When Professor Jørgensen attempted (Angew. Chem. Int. Ed. 2008, 47, 121) the related addition of 14 and 15 using catalyst 3a, he did not observe the expected Michael-Michael sequence. Rather, the initial Michael addition was followed by a Morita-Baylis-Hillman condensation, to give 16. The β-keto ester 16 existed primarily in its enol form. Organocatalysts can also be used to prepare polycyclic systems. Professor Jørgensen has found (Chem. Commun. 2008, 3016) that condensation of 14 with acetone dicarboxylate 17, again using catalyst 3a, gave the bicyclic β-keto ester 18. Matthew J. Gaunt of the University of Cambridge observed (J. Am. Chem. Soc. 2008, 130, 404) that for the cyclization of 19, catalyst 3b was superior to catalyst 3a. The power of desymmetrization of prochiral intermediates was illustrated by the report (J. Am. Chem. Soc. 2008, 130, 6737) from Benjamin List of the Max-Planck-Institute, Mülheim of the cyclization of 21 to 23. Organocatalysts can also be used to prepare larger rings.

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