Functionalization and Homologation of C-H Bonds

Author(s):  
Douglass F. Taber

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.

Author(s):  
Douglass F. Taber

Masayuki Inoue of the University of Tokyo oxidized (Tetrahedron Lett. 2011, 52, 4654) the alkyl benzene 1 to the nitrate 2, which could be carried on to the amide 5, the nitrile 6, the alcohol 7, or the azide 8. X. Peter Zhang of the University of South Florida developed (Chem. Sci. 2012, 2, 2361) a Co catalyst for the cyclization of 7 to 8. Justin Du Bois of Stanford University reported (J. Am. Chem. Soc. 2011, 133, 17207) the oxidative cyclization of the sulfamate corresponding to 7 using a Ru catalyst. Seongmin Lee of the University of Texas showed (Org. Lett. 2011, 13, 4766) that the oxidative cyclization of 9 gave the amine 10 with high diastereoselectivity. Fabrizio Fabris of the Università di Venezia used (Tetrahedron Lett. 2011, 52, 4478) a Ru catalyst to oxidize 11 to the ketone 12. Ying-Yeung Yeung of the National University of Singapore found (Org. Lett. 2011, 13, 4308) that hypervalent iodine was sufficient to oxidize 13 to the ketone 14. Huanfeng Jiang of the South China University of Technology methoxycarbonylated (Chem. Commun. 2011, 47, 12224) 15 under Pd catalysis to give 16. Professor Inoue found (Org. Lett. 2011, 13, 5928) that the oxidative cyanation of 17 proceeded with high diastereoselectivity to give 18. Mamoru Tobisu and Naoto Chatani of Osaka University activated (J. Am. Chem. Soc. 2011, 133, 12984) 19 with a Pd catalyst to enable coupling with 20 to give 21. Rh-mediated intramolecular insertion is well known to proceed efficiently into secondary and tertiary C–H bonds. A. Srikrishna of the Indian Institute of Science, Bangalore found (Synlett 2011, 2343) that insertion into the methyl C–H of 22 also worked smoothly to deliver 23. The macrocyclic oligopeptide valinomycin 24 has nine isopropyl groups. It is remarkable, as observed (Org. Lett. 2011, 13, 5096) by Cosimo Annese of the Università di Bari and Paul G. Williard of Brown University, that direct oxidation of 24 with methyl(trifluoromethyl) dioxirane in acetone specifically hydroxylated at 8 (45.5%, our numbering), 7 (28.5%), and 6 (26%).


Author(s):  
Douglass F. Taber

Terminal epoxides such as 1 are readily available in high enantiomeric excess. Christopher D. Bray of Queen Mary University of London observed (Tetrahedron Lett. 2014, 55, 5890) clean inversion in the conversion of 1 to the aziridine 3 with the reagent 2. Yong-Chun Luo and Peng-Fei Xu of Lanzhou University opened (Org. Lett. 2014, 16, 4896) the activated cyclopropane 4 with benzyl azide, then heated the adduct to expel N2, leading to the azetidine 5. Zhenming Du of Roche Shanghai and Michelangelo Scalone of Roche Basel devel­oped (Org. Process Res. Dev. 2014, 18, 1702) practical conditions for the asymmetric hydrogenation of 6 to the pyrrolidine 7. Young Ho Rhee of the Pohang University of Science and Technology showed (Chem. Eur. J. 2014, 20, 16391) that depending on the diol protecting group, addition of allyl silane to 8 could lead to either the cis product 9 or the trans diastereomer (not illustrated). Ohyun Kwon of UCLA used (J. Am. Chem. Soc. 2014, 136, 11890) an organocatalyst to add the racemic allene 10 to 11 to give 12 in high ee. Tom Livinghouse of Montana State University cyclized (Angew. Chem. Int. Ed. 2014, 53, 14352) the hydrazine 13 into an intermediate organozinc species that was then coupled with allyl bromide to give 14. Yonggang Chen of Merck Process and Xumu Zhang of Rutgers University devised (Angew. Chem. Int. Ed. 2014, 53, 12761) practical conditions for the reduction of 15 to the piperidine 16. Teck-Peng Loh of the Nanyang Technological University and the University of Science and Technology of China effected (Chem. Commun. 2014, 50, 8324) asymmetric phenylation of biomass-derived 17 to give an intermediate that was oxidatively rearranged, then reduced to 18. Robert R. Knowles of Princeton University showed (J. Am. Chem. Soc. 2014, 136, 12217) that the cyclization of 19 to 20 proceeded with high diastereoselectivity. Maria J. Alves of the Universidade do Minho osmylated (Synlett 2014, 25, 1751) the adduct from the Diels–Alder cycload­dition of 22 to 21 to give 23 in high ee.


Author(s):  
Douglass F. Taber

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.


Author(s):  
Douglass F. Taber

Akio Saito and Yuji Hanzawa of Showa Pharmaceutical University found (Tetrahedron Lett. 2011, 52, 4658) that an alkynyl keto ester 1 could be oxidatively cyclized to the furan 2. Eric M. Ferreira of Colorado State University showed (Org. Lett. 2011, 13, 5924) that depending on the conditions, a Pt catalyst could cyclize 3 to either 4 or 5. Shunsuke Chiba of Nanyang Technological University used (J. Am. Chem. Soc. 2011, 133, 13942) Cu catalysis for the oxidation of 6 to the pyrrole 7. Vladimir Gevorgyan of the University of Illinois at Chicago devised (Org. Lett. 2011, 13, 3746) a convergent assembly of the pyrrole 10 from the alkyne 8 and the alkyne 9. Dale L. Boger of Scripps La Jolla extended (J. Am. Chem. Soc. 2011, 133, 12285) the scope of the Diels-Alder addition of the triazine 11 to an alkyne 12 to give the pyridine 13. Tomislav Rovis, also of Colorado State University, used (Chem. Commun. 2011, 47, 11846) a Rh catalyst to add an alkyne 15 to the oxime 14 to give the pyridine 16. Sensuke Ogoshi of Osaka University, under Ni catalysis, added (J. Am. Chem. Soc. 2011, 133, 18018) a nitrile 18 to the diene 17 to give the pyridine 19. Alexander Deiters of North Carolina State University showed (Org. Lett. 2011, 13, 4352) that the complex tethered diyne 20 combined with 21 with high regiocontrol to give 22. Yong-Min Liang of Lanzhou University prepared (J. Org. Chem. 2011, 76, 8329) the indole 24 by cyclizing the alkyne 23. Xiuxiang Qi and Kang Zhao of Tianjin University found (J. Org. Chem. 2011, 76, 8690) that the enamine 25 could be oxidatively cyclized to the indole 26. Kazuhiro Yoshida and Akira Yanagisawa of Chiba University established (Org. Lett. 2011, 13, 4762) that ring-closing metathesis converted the keto ester 27 to the indole 28. Alessandro Palmieri and Roberto Ballini of the Università di Camerino observed (Adv. Synth. Catal. 2011, 353, 1425) that the pyrrole 30 spontaneously added to the nitro acrylate 29 to give an adduct that cyclized to 31 on exposure to acid.


Author(s):  
PHILIP VAN BEYNE ◽  
VANDA CLAUDINO-SALES ◽  
SAULO ROBERTO DE OLIVEIRA VITAL ◽  
DIEGO NUNES VALADARES

In its third edition, the “William Morris Davis – Journal of Geomorphology” presents its second interview with geographers, to head the “Interviews” section, which opens each published issue. This time, it is the first international interview, carried out with Professor Philip van Beynen, from the University of South Florida, in the United States. Professor Philip van Beynen was interviewed on the topic “Karst in Urban Areas”, and brings important data on the subject, with beautiful illustrations and with examples from all over the world. The interview took place on September 17, 2020, with the participation of Vanda de Claudino-Sales (Professor of the Academic Master in Geography at the State University of Vale do Acarau-UVA) and Saulo Roberto Oliveira Vital (Professor of the Department of Geography and the Post-Graduate Program in Geography at the Federal University of Paraiba - UFPB), and was transcribed by Diego Nunes Valadares, master's student on Geography at the Federal University of Rio Grande do Norte. Professor van Beynen was born in New Zealand, where he received his degree in Geography at the University of Auckland. He earned a master's degree from the same university, and a doctorate and post-doctorate from McMaster University, Canada. He has been a professor at the School of Geoscience at the University of South Florida since 2009, where he   has been developing research related to different components of karst environments. The interview shows his great expertise on the subject, and is very much worth to be read and seen even for those who are not specialists in karst.


Author(s):  
Douglass Taber

There continue to be new developments in transition metal- and lanthanide-mediated construction of carbocycles. Although a great deal has been published on the asymmetric cyclopropanation of styrene, relatively little had been reported for other classes of alkenes. Tae-Jeong Kim of Kyungpook National University has devised (Tetrahedron Lett. 2007, 48, 8014) a Ru catalyst for the cyclopropanation of simple α-olefins such as 1. X. Peter Zhang of the University of South Florida has developed (J. Am.Chem. Soc. 2007, 129, 12074) a Co catalyst for the cyclopropanation of alkenes such as 5 having electron-withdrawing groups. Alexandre Alexakis of the Université de Genève has reported(Angew. Chem. Int. Ed. 2007, 46, 7462) simple monophosphine ligands that enabled enantioselective conjugate addition to prochiral enones, even difficult substrates such as 8. Seunghoon Shin of Hanyang University has found (Organic Lett. 2007, 9, 3539) an Au catalyst that effected the diastereoselective cyclization of 10 to the cyclohexene 11, and Radomir N. Saicic of the University of Belgrade has carried out (Organic Lett. 2007, 9, 5063), via transient enamine formation, the diastereoselective cyclization of 12 to the cyclohexane 13. Alois Fürstner of the Max-Planck- Institut, Mülheim has devised (J. Am. Chem. Soc. 2007, 129, 14836) a Rh catalyst that cyclized the aldehyde 14 to the cycloheptenone 15. Some of the most exciting investigations reported in recent months have been directed toward the direct diastereo- and enantioselective preparation of polycarbocyclic products. Rai-Shung Liu of National Tsing-Hua University has extended (J. Org. Chem. 2007, 72, 567) the intramolecular Pauson-Khand cyclization to the epoxy enyne 16, leading to the 5-5 product 17. Michel R. Gagné of the University of North Carolina has devised (J. Am. Chem. Soc. 2007, 129, 11880) a Pt catalyst that smoothly cyclized the polyene 18 to the 6-6 product 19. Yoshihiro Sato of Hokkaido University and Miwako Mori of the Health Science University of Hokkaido have described (J. Am. Chem. Soc. 2007, 129, 7730) a Ru catalyst for the cyclization of 20 to the 5-6-5 product 21. Each of these processes proceeded with high diastereocontrol.


Author(s):  
Douglass F. Taber

Varinder K. Aggarwal of the University of Bristol described (Angew. Chem. Int. Ed. 2010, 49, 6673) the conversion of the Sharpless-derived epoxide 1 into the cyclopropane 2. Christopher D. Bray of Queen Mary University of London established (Chem. Commun. 2010, 46, 5867) that the related conversion of 3 to 5 proceeded with high diastereocontrol. Javier Read de Alaniz of the University of California, Santa Barbara, extended (Angew. Chem. Int. Ed. 2010, 49, 9484) the Piancatelli rearrangement of a furyl carbinol 6 to allow inclusion of an amine 7, to give 8. Issa Yavari of Tarbiat Modares University described (Synlett 2010, 2293) the dimerization of 9 with an amine to give 10. Jeremy E. Wulff of the University of Victoria condensed (J. Org. Chem. 2010, 75, 6312) the dienone 11 with the commercial butadiene sulfone 12 to give the highly substituted cyclopentane 13. Robert M. Williams of Colorado State University showed (Tetrahedron Lett. 2010, 51, 6557) that the condensation of 14 with formaldehyde delivered the cyclopentanone 15 with high diastereocontrol. D. Srinivasa Reddy of Advinus Therapeutics devised (Tetrahedron Lett. 2010, 51, 5291) conditions for the tandem conjugate addition/intramolecular alkylation conversion of 16 to 17. Marie E. Krafft of Florida State University reported (Synlett 2010, 2583) a related intramolecular alkylation protocol. Takao Ikariya of the Tokyo Institute of Technology effected (J. Am. Chem. Soc. 2010, 132, 11414) the enantioselective Ru-mediated hydrogenation of bicyclic imides such as 18. This transformation worked equally well for three-, four-, five-, six-, and seven-membered rings. Stefan France of the Georgia Institute of Technology developed (Org. Lett. 2010, 12, 5684) a catalytic protocol for the homo-Nazarov rearrangement of the doubly activated cyclopropane 20 to the cyclohexanone 21. Richard P. Hsung of the University of Wisconsin effected (Org. Lett. 2010, 12, 5768) the highly diastereoselective rearrangement of the triene 22 to the cyclohexadiene 23. Strategies for polycyclic construction are also important. Sylvain Canesi of the Université de Québec devised (Org. Lett. 2010, 12, 4368) the oxidative cyclization of 24 to 25.


Author(s):  
Douglass F. Taber

Adriaan J. Minnaard and Ben L. Feringa of the University of Groningen devised (J. Am. Chem. Soc. 2010, 132, 14349) what promises to be a general strategy for the construction of enantiomerically pure cyclopropanes, based on conjugate addition to acceptors such as 1 . X. Peter Zhang of the University of South Florida developed (J. Am. Chem. Soc. 2010, 132, 12796) a Co catalyst for the enantioselective cyclopropanation of α-olefins such as 3. Seiji Iwasa of Toyohashi University of Technology designed (Angew. Chem. Int. Ed. 2010, 49, 8439) a resin-bound Ru catalyst that could be used repeatedly for the enantioselective cyclization of the ester 6. Rai-Shung Lin of National Tsing-Hua University showed (Angew. Chem. Int. Ed. 2010, 49, 9891) that a gold catalyst could expand the alkyne 8 to the cyclobutene 9. Takao Ikariya of the Tokyo Institute of Technology reported (J. Am. Chem. Soc. 2010, 132, 16637) a detailed study of the enantioselective conjugate addition of malonate 11 to cyclopentenone 10. Vladimir A. D’yakonov of the Russian Academy of Sciences, Ufa, showed (Tetrahedron Lett. 2010, 51, 5886) that a cyclic alkyne 13 could be annulated to the cyclopentenone 14. Shunichi Hashimoto of Hokkaido University also designed (Angew. Chem. Int. Ed. 2010, 49, 6979) a resin-bound Rh catalyst that could also be used repeatedly for the enantioselective cyclization of the ester 15. Tushar Kanti Chakraborty of the Central Drug Research Institute used (Tetrahedron Lett. 2010, 51, 4425) Ti(III) to mediate the diastereoselective cyclization of 17 to 18. Alexandre Alexakis of the University of Geneva extended (Synlett 2010, 1694) enantioselective conjugate addition of isopropenyl to the more difficult enone 19. Joseph P. A. Harrity of the University of Sheffield showed (Org. Lett. 2010, 12, 4832) that Pd could catalyze the rearrangement of 21 to 22. Strategies for the controlled construction of polycyclic ring systems are also important. Günter Helmchen of the Universität Heidelberg showed (J. Org. Chem. 2010, 75, 7917) that 23 was efficiently cyclized to the diene with Pt catalyst. The reaction could be carried out in the presence of the dienophile 24 to give 25 directly.


Author(s):  
Junghwan Kim ◽  
Heh Youn Shin ◽  
Kim L. Smith ◽  
Jihee Hwang

This chapter examines two U.S. four-year public universities, the Pennsylvania State University World Campus and the University of Oklahoma Outreach, that have successfully developed online adult education system/programs for adults. Using the principles of effectiveness for serving adult learners, the integrated review reveals not only how they advance online higher education environment for adults, but the types of challenges they have. Key findings highlight that, under a strong tradition of distance education, “self-assessment system,” “financial independence,” and “diverse active supports for life and career planning” play a critical role in increasing the academic engagement and retention of adult students. However, they also have several challenges: “high tuition rates and limited scholarship options,” “monitoring students' experience,” “learning outcome assessment,” and “commitment of faculty members.” The authors close with practical/academic implications and future research agendas.


Author(s):  
Douglass F. Taber

Xin-Yan Wu of East China University of Science and Technology and Jun Yang of the Shanghai Institute of Organic Chemistry added (Tetrahedron Lett. 2014, 55, 4071) the Grignard reagent 1 to propargyl alcohol 2 to give an intermediate that could be bory­lated, then coupled under Pd catalysis with an anhydride, leading to the furan 3. Fuwei Li of the Lanzhou Institute of Chemical Physics constructed (Org. Lett. 2014, 16, 5992) the furan 6 by oxidizing the keto ester 4 in the presence of the enamide 5. Yuanhong Liu of the Shanghai Institute of Organic Chemistry prepared (Angew. Chem. Int. Ed. 2014, 53, 11596) the pyrrole 9 by reducing the azadiene 7 with the Negishi reagent, then adding the nitrile 8. Yefeng Tang of Tsinghua University found (Tetrahedron Lett. 2014, 55, 6455) that the Rh carbene derived from 11 could be added to an enol silyl ether 10 to give the pyrrole 12. Pazhamalai Anbarasan of the Indian Institute of Technology Madras reported (J. Org. Chem. 2014, 79, 8428) related results. Zheng Huang of the Shanghai Institute of Organic Chemistry established (Angew. Chem. Int. Ed. 2014, 53, 1390) a connection between substituted piperidines and pyridines by dehydrogenating 13 to 15, with 14 as the acceptor. Joseph P. A. Harrity of the University of Sheffield conceived (Chem. Eur. J. 2014, 20, 12889) the cascade assembly of the pyridine 18 by cycloaddition of 16 with 17 followed by Pd-catalyzed coupling. Teck-Peng Loh of Nanyang Technological University converted (Org. Lett. 2014, 16, 3432) the keto ester 19 into the azirine, then eliminated it to form an aza­triene that cyclized to the pyridine 20. En route to a cholesteryl ester transfer protein inhibitor, Zhengxu S. Han of Boehringer Ingelheim combined (Org. Lett. 2014, 16, 4142) 21 with 22 to give an intermediate that could be oxidized to 23. Magnus Rueping of RWTH Aachen used (Angew. Chem. Int. Ed. 2014, 53, 13264) an Ir photoredox catalyst in conjunction with a Pd catalyst to cyclize the enamine 24 to the indole 25. Yingming Yao and Yingsheng Zhao of Soochow University effected (Angew. Chem. Int. Ed. 2014, 53, 9884) oxidative cyclization of 26 to 27.


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