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Monday, September 29, 2014
Douglass F. Taber
University of Delaware

Organic Functional Group Protection and Deprotection

Martin Oestreich of the Technische Universität Berlin developed (Eur. J. Org. Chem. 2014, 2077. ) the Birch reduction product 2 as a donor for the silylation of an alcohol 1. Atahualpa Pinto of the SUNY College of Environmental Science and Forestry devised (Tetrahedron Lett. 2014, 55, 2600. ) conditions for the monosilylation of the diol 4. Quanxuan Zhang of Michigan State University reported (Tetrahedron Lett. 2014, 55, 3384. ) the preparation (not illustrated) of the mono-THP ethers of symmetrical diols. The product from the Mitsunobu coupling of an acid with an alcohol 6 can be difficult to purify. Takashi Sugimura of the University of Hyogo showed (Synthesis 2013, 45, 931. ) that the oxidation product from 7 and the reduction product from 8 could both be removed from the product 9 by simple extraction.

David Milstein of the Weizmann Institute of Science found (Angew. Chem. Int. Ed. 2014, 53, 4685. ) that an Fe catalyst could be used to reduce the trifluoroacetate 10 to 11. Jean-Michel Vatèle of the Université Lyon 1 oxidized (Synlett 2014, 25, 115. ) the benzylidene acetal 12 selectively to the monobenzoate 13. Xinyu Liu of the University of Pittsburgh organized (Chem. Commun. 2014, 50, 3155. ) a family of acid-sensitive esters that can be selectively removed in the presence of other esters, as exemplified by the conversion of 14 to 15.

Ryo Yazaki and Takashi Ohshima of Kyushu University observed (Angew. Chem. Int. Ed. 2014, 53, 1611. ) that an amine 16 would add spontaneously to acrylonitrile 17 to give 18. In the presence of a Cu catalyst, alcohols added to 17 even more readily. Diego Gamba-Sánchez of the Universidad de los Andes used (J. Org. Chem. 2014, 79, 4544. ) simple Fe catalysts to activate a wide range of amides, including 20, to become acylating agents.

1,2-Addition to t-butylsulfanylimines is widely used to construct aminated stereogenic centers. Xiaodong Yang and Hongbin Zhang of Yunnan University established (Chem. Commun. 2014, 50, 6259. ) a general protocol for cleaving the N-S bond in the product 22 to give the desired free amine 23. John A. Murphy of the University of Strathclyde demonstrated (J. Org. Chem. 2014, 79, 3731, ; Angew. Chem. Int. Ed. 2014, 53, 474, ) many applications for the powerful photoreductant 25, including the deprotection of the sulfonamide 24 to give the free amine 26.

Willi Bannwarth of the Albert-Ludwigs-Universität Freiburg created (Chem. Eur. J. 2014, 20, 1258. ) an expanded family of chelating amides that could be selectively activated with Fe, Zn and Cu respectively. Dirk Trauner of the Ludwig-Maximilian-Universität München observed (Tetrahedron Lett. 2014, 55, 59. ) that an Evans acyl oxazolidinone aldol product could easily be cleaved if it was first converted into the xanthate 29. N. Jung and Stefan Bräse of the Karlsruhe Institute of Technology devised (Org. Lett. 2014, 16, 1036. ) an odorless polymeric reagent for the conversion of an aldehyde 31 to the dithiane 32. José Vicente of the Universidad de Murcia found (Tetrahedron Lett. 2014, 55, 1141. ) Pd-catalyzed conditions for the deprotection of 33 without dehydration of the sensitive tertiary alcohol.

D. F. Taber, Org. Chem. Highlights 2014, September 29.