Gold-catalyzed efficient synthesis of azepan-4-ones via a two-step [5 + 2] annulation
作者:Li Cui、Longwu Ye、Liming Zhang
DOI:10.1039/c001314e
日期:——
A surprisingly efficient synthesis of azepan-4-ones via a two-step [5â+â2] annulation is developed. This reaction involves a key gold catalysis and shows generally high regioselectivities and good to excellent diastereoselectivities.
Published as part of the Special Topic Modern Cyclization Strategies in Synthesis Abstract A transition-metal-free silane–iodine catalytic system comprising I2 and Et3SiH promotes intramolecular hydroalkoxylation/reduction and hydroamination/reduction of unactivated alkynes. This system allows the reaction to proceed at room temperature affording 2,4- and 2,5-disubstituted pyrrolidines as well as a
Tandem hydroalkoxylation/hydroallylation and hydroalkoxylation/hydrocyanation reactions of alkyl-substituted unactivated alkynes by catalytic systems based on B(C6F5)3·nH2O and silyl nucleophiles were developed. The characteristic high alkynophilicity of B(C6F5)3 enabled the selective activation of the unactivated alkynes in the presence of the reactive alkene of allylsilane. Moreover, the alkynes
基于B(C 6 F 5)3 · n H 2 O和甲硅烷基亲核试剂的催化体系,开发了烷基取代的未活化炔烃的串联加氢烷氧基化/加氢芳基化和加氢烷氧基化/加氢氰化反应。B(C 6 F 5)3的特征性高亲核性使它能够在烯丙基硅烷的反应性烯烃存在下选择性活化未活化的炔烃。此外,在该催化体系中,在氰化物存在下,炔烃被亲电活化。机理研究表明,炔烃在两个反应中被不同的催化物种活化。
Highly Regio- and Stereoselective Hydrostannylation of Alkynols with A New Lewis Acidic Hydrostannane
Bu2Sn(OTf)H (1a), easily prepared from Bu2SnH2 and TfOH, was found to be very valuable for highly regio- and stereoselective hydrostannylation of various propargyl alcohols leading to (Z)-gamma-stannylated allyl alcohols. The stannylation with la is applicable to the synthesis of hydroxysubstituted (Z)-vinylstannanes from terminal alkynes bearing a hydroxy group at the homoallylic or bishomoallylic position. The coordination of the hydroxy group to the Lewis acidic tin center plays an important role for the observed regio- and stereochemistry.