Monday, June 8, 2015
Douglass F. Taber
University of Delaware
Organic Functional Group Protection
Sentaro Okamoto of Kanagawa University developed (Tetrahedron Lett. 2014, 55, 7039. ) an organocatalyst that mediated the selective acylation of 1 to give the primary acetate 2. Philip A. Albiniak of Ball State University devised (Tetrahedron Lett. 2014, 55, 7133. ) a reagent for the simple preparation of a t-butyl ether 5 from an alcohol 3.
Attempted deprotection of 6 tended to divert to the dioxolane. Toshio Nishikawa of Nagoya University developed (Synlett 2014, 25, 2498. ) an oxidative protocol that gave clean conversion to the desired 7. Alan S. Goodman of Rutgers University found (Angew. Chem. Int. Ed. 2014, 53, 10160. ) an Ir catalyst that generated the phenol 9 from the aryl alkyl ether 8.
In the course of a synthesis of Sch 725674, Kavirayani R. Prasad of the Indian Institute of Science, Bangalore deprotected (Org. Lett. 2014, 16, 4001. ) the dithiane 10 to yield the sensitive aldol product 11. Karl Anker J°rgensen of Aarhus University observed (Chem. Commun. 2014, 50, 15689. ) that the nitro isoxazole 12, having served to activate sequential Michael addition, was readily cleaved to the acid 13.
Jiang Cheng of Changzhou University used (Chem. Commun. 2014, 50, 8412. ) CuCN to convert 14 to 15. Pradeep Kumar of CSIR-National Chemistry Laboratory effected (Tetrahedron Lett. 2014, 55, 7172. ) oxidative deallylation of 16, leading to 17. Hiroyuki Morimoto and Takashi Ohshima of Kyushu University found (Chem. Commun. 2014, 50, 12623. ) that NH4I promoted the hydrazinolysis of the amide 18, giving 19 without racemization. Franco Ghelfi of the UniversitÓ degli Studi di Modena e Reggio Emilia prepared (Eur. J. Org. Chem. 2014, 6734. ) 21 by desulfonylating 20 with H2SO4 in acetic acid. Hans Adolfsson of Stockholm University reduced (Org. Lett. 2014, 16, 680. ) the amide 22 to the enamine 23. The N-vinyl amine could be hydrolyzed, but it is also a versatile intermediate for other transformations.
Automated peptide synthesis can be hindered by difficult sequences. Judit Tulla-Puche and Fernando Albericio of IRB Barcelona showed (Chem. Eur. J. 2014, 20, 15031. ) that the substituted benzyl group of 24 facilitated such syntheses, and that it could be readily removed by exposure to NH4I and trifluoroacetic acid.
Akihiro Orita of the Okayama University of Science demonstrated (Chem. Lett. 2014, 43, 1610. ) that the diphenylphosphoryl group of 26 was orthogonal to the alternative silyl protection. Silyl alkynes were stable to CH3MgBr, and 26 was stable to TBAF and to AgBF4, reagents that desilylated terminal alkynes.
The cyclic alkyne of 28 is much more reactive than the terminal alkyne. Suguru Yoshida and Takamitsu Hosoya of the Tokyo Medical and Dental University found (J. Am. Chem. Soc. 2014, 136, 13590. ) that click chemistry could be selectively carried out on the terminal alkyne if the cyclic alkyne was first protected as the stoichiometric Cu complex 29.
D. F. Taber, Org. Chem. Highlights 2015, June 8.