π-Facial Diastereoselection in Diels−Alder Reactions of (R)-4-[(p-Tolylsulfinyl)methyl]quinols
摘要:
Diels-Alder reactions of a range of (R)-4-hydroxy-4-[(p-tolylsulfinyl)methyl]-2,5-cyclohexadienones with cyclopentadiene and 1,3-pentadiene proceed in a total pi-facial diastereoselective manner from the C-4 OH side. Ab initio calculations at the RHF/6-31G* theory level provide data on transition-state energies for cycloadditions with cyclopentadiene in full agreement with the experimental results.
Synthesis of Azobenzenes from Quinone Acetals and Arylhydrazines
作者:M. Carmen Carreño、Gerardo Fernández Mudarra、Estíbaliz Merino、María Ribagorda
DOI:10.1021/jo0498011
日期:2004.5.1
Direct reaction between quinone bisacetals and arylhydrazines gives azobenzenes. The presence of catalytic amounts of cerium ammonium nitrate strongly accelerates the reaction. When the bisacetal has a substituent at the 2,5-cyclohexadiene framework, only one regioisomer is formed. The method represents a simple, mild, and novel synthetic access to differently substituted azocompounds in high to excellent