Preparation of methyl carbamates from primary alkyl- and arylcarboxamides using hypervalent iodine
摘要:
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.
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.
Synthesis of 7-Azabicyclo[2.2.1]heptane and 2-Oxa-4-azabicyclo[3.3.1]non-3-ene Derivatives by Base-Promoted Heterocyclization of Alkyl <i>N</i>-(<i>cis</i>(<i>trans</i>)-3,<i>trans</i>(<i>cis</i>)-4-Dibromocyclohex-1-yl)carbamates and <i>N</i>-(<i>cis</i>(<i>trans</i>)-3,<i>trans</i>(<i>cis</i>)-4-Dibromocyclohex-1-yl)-2,2,2-trifluoroacetamides
trans-4-dibromocyclohex-1-yl)carbamate (10) with sodium hydride in DMF at room temperature provides 2-bromo-7-[(tert-butoxy)carbonyl]-7-azabicyclo[2.2.1]heptane (2) (52% yield), whose t-BuOK-promoted hydrogen bromide elimination affords 7-[(tert-butoxy)carbonyl]-7-azabicyclo[2.2.1]hept-2-ene (31) in 78% yield, an intermediate in the total synthesis of epibatidine (1). However, the NaH/DMF-mediated heterocyclization