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Monday, June 13, 2016
Douglass F. Taber
University of Delaware

Organic Functional Group Protection

Masahito Murai and Kazuhiko Takai of Okayama University developed (Org. Lett. 2015, 17, 3346. ) a Re catalyst for the deoxygenation of an epoxide 1 to the alkene 2. Naseem Ahmed of the Indian Institute of Technology, Roorkee devised (Synthesis 2015, 47, 3542. ) an alternative Sn-based epoxide deoxygenation (not illustrated). Adrian Ortiz of Bristol-Myers Squibb effected (Angew. Chem. Int. Ed. 2015, 54, 7185. ) facile elimination of the sulfide 3 to the alkene 4.

Daniel E. Falvey of the University of Maryland established (Org. Lett. 2015, 17, 5986. ) that the ether 5 could be converted to the free alcohol 6 with UV irradiation, or, in the presence of a transition metal photocatalyst, with visible light. The catalyst 8 devised (Adv. Synth. Catal. 2015, 357, 3825. ) by Alan C. Spivey of Imperial College London allowed the ready formation of the silyl ether 10 from even very hindered alcohols such as 7.

Anikó Borbás of the University of Debrecen found (Eur. J. Org. Chem. 2015, 5730. ) a reagent combination that reduced the acetal 11 selectively to the ether 12 without concomitant reduction of the butane diacetal. Károly Agoston, now at Carbosynth LTD, developed (Tetrahedron Lett. 2015, 56, 5010. ) a set of carbohydrate protecting groups that could be removed orthogonally one to another, as exemplified by the conversion of 13 to 14.

Georg Manolikakes of the Goethe-Universität Frankfurt established (Eur. J. Org. Chem. 2015, 4624. ) a reliable method for preparing the N,O-acetal 17 by combining a primary amide 15 with an aldehyde 16. Marco Pallavicini of the Universitŕ degli Studi di Milano showed (Org. Process Res. Dev. 2015, 19, 878. ) that azeotropic removal of water with cyclohexane allowed the conversion of 18 to 19 with full maintenance of enantiomeric excess.

As illustrated by the conversion of 20 to 21 reported (Chem. Eur. J. 2015, 21, 11219. ) by Stefan Bräse of the Karlsruhe Institute of Technology, a carboxylic acid can be masked as a 2-furyl group. The facile conversion of the amide 22 to the ester 23 reported (Nature 2015, 524, 79. ) by K. N. Houk and Neil K. Garg of UCLA can be seen as a method for deprotecting amines, or acids.

Sanghapal D. Sawant of the Indian Institute of Integrative Medicine demonstrated (Tetrahedron Lett. 2015, 56, 4775. ) the facile transamidation of 24 to 25. Masato Kitamura of Nagoya University directly incorporated (Chem. Commun. 2015, 51, 13110. ) carbon dioxide for the conversion of 26 to 27. In a parallel development, Chaorong Qi and Huanfeng Jiang of the South China University of Technology used (Chem. Eur. J. 2015, 21, 14314. ) carbon dioxide to protect the amine 28 as the carbamate 29.

David Crich of Wayne State University converted (Org. Lett. 2015, 17, 4006. ) 30 selectively to 31 by taking advantage of the instability of aryl triazenes derived from primary amines. Both of the amines initially reacted with the diazonium salt, but only the triazene of the secondary amine was stable to subsequent handling.

D. F. Taber, Org. Chem. Highlights 2016, June 13.
URL: http://www.organic-chemistry.org/Highlights/2016/13June.shtm