Preparation of methyl carbamates from primary alkyl- and arylcarboxamides using hypervalent iodine
作者:Robert M. Moriarty、Calvin J. Chany、Rahde K. Vaid、Om Prakash、Sudersan M. Tuladhar
DOI:10.1021/jo00061a022
日期:1993.4
A series of 14 primary alkyl- and arylcarboxamides were treated with PhI(OAc)2 in KOH-CH3OH at 5-10-degrees-C to give the corresponding methyl carbamates in good to excellent yields. These conditions avoid the use of elemental bromine or heavy metal reagents (Pb(OAc)4, AgOAc, Hg(OAC)2), while taking advantage of the commercial availability of PhI(OAc)2. The methyl carbamates are easily purified via column chromatography on silica gel. The isolated yields of the carbamates ranged from 72 % for methyl N-cyclopropylcarbamate to 97 % for methyl N-phenylcarbamate.
Reductive cyclization of carbon-centered glycine radicals; a novel synthetic route to cyclic α-amino acids
作者:Peter M. Esch、Henk Hiemstra、Richard F. de Boer、W.Nico Speckamp
DOI:10.1016/s0040-4020(01)81240-0
日期:1992.1
Reductive cyclizations (tributylin hydride, AIBN) of several α-(penthylthio)glycine derivatives with a 30alkenyl substituent at nitrogen are reported. These reactions proceed via 2-aza-5-alken-1-yl radicals as intermediates which bear electron-withdrawing carbonyl substituents at the radical center and at nitrogen. Such radicals can be considered as relatively stable captodative radicals, but are reactive