Stereoselective Intermolecular Carbolithiation of Open-Chain and Cyclic 1-Aryl-1-alkenyl N,N-Diisopropylcarbamates Coupled with Electrophilic Substitution. Observation of p-Carboxylation in a Benzyllithium Derivative
作者:Jan Georg Peters、Michael Seppi、Roland Fröhlich、Birgit Wibbeling、Dieter Hoppe
DOI:10.1055/s-2002-20040
日期:——
1-Aryl-1-alkenyl N,N-diisopropylcarbamates (1) are obtained from alkyl aryl ketones and N,N-diisopropylcarbamoyl chloride (CbCl) by heating with excess pyridine. These undergo facile syn-carbolithiation by alkyllithium/diamine and produce configurationally stable lithiated benzyl carbamates, which have been trapped with different electrophiles. If the reaction is carried out in the presence of chiral
Treatment of alkenyl carbamates with sodium dispersion and a co-existing boron electrophile affords alkenylboronates via the reductive cleavage of the vinylic C–Obond. The key to this borylation is an instant trapping of reactive organosodium species with the co-existing boron electrophile.