A facile and convenient protocol for the synthesis of cinnamides from cinnamic acids and tetraalkylthiuram disulfides under metal and additive free conditions has been achieved. This method allows the efficient coupling of diverse cinnamic acids with tetraalkylthiuram disulfides through a simply mixing operation.
Stereospecific Cyclopropanation of Highly Substituted C−C Double Bonds Promoted by CrCl<sub>2</sub>. Stereoselective Synthesis of Cyclopropanecarboxamides and Cyclopropyl Ketones
作者:José M. Concellón、Humberto Rodríguez-Solla、Carmen Méjica、Elena G. Blanco
DOI:10.1021/ol070896d
日期:2007.8.1
(Z)-alpha,beta-enamides in which the C-C double bond is di-, tri-, or tetrasubstituted. In all cases the process is completely stereospecific and only a single diastereoisomer is obtained. In addition, cyclopropyl ketones were readily prepared by reaction of the cyclopropanecarboxamides (derived from morpholine) obtained with a range of organolithium compounds. A mechanism has been proposed to explain the cyclopropanation
CrCl<sub>2</sub>-Promoted Stereospecific and Stereoselective Alkyl- and Silylcyclopropanation of α,β-Unsaturated Amides
作者:José M. Concellón、Humberto Rodríguez-Solla、Carmen Méjica、Elena G. Blanco、Santiago García-Granda、M. Rosario Díaz
DOI:10.1021/jo800103t
日期:2008.5.1
An efficient chromium-promoted alkyl- or silylcyclopropanation of α,β-unsaturated amides is described. These reactions can be carried out on (E)- or (Z)-α,β-enamides in which the C−C double bond is di-, or trisubstituted. This process takes place with totalstereospecificity and the new stereogenic center is generated with high or total stereoselectivity. Some synthetic applications of the obtained
Highly Stereoselective Halocyclopropanation of α,β-Unsaturated Amides
作者:José M. Concellón、Humberto Rodríguez-Solla、Elena G. Blanco、María A. Villa-García、Noemí Alvaredo、Santiago García-Granda、M. Rosario Díaz
DOI:10.1002/adsc.200900331
日期:2009.9
A convenient highly stereoselective synthesis of chloro- and bromocyclopropanamides from di- tri- or tetrasubstituted (E)- or (Z)-α,β-unsaturatedamides with total or high stereoselectivity promoted by chromium dichloride or dibromide is described. The transformation of chlorocyclopropanamides into the corresponding ketones or amines is also reported. A mechanism to explain these transformations is
Stereoselective beta -elimination of 2-chloro-3-hydroxyamides 1 is achieved by using samarium diiodide to yield alpha,beta -unsaturated amides 2, in which the C=C bond is di- tri-, or tetrasubstituted. The starting compounds a are easily prepared by reaction of the corresponding lithium enolates of alpha -chloroamides with aldehydes or ketones at -78 degreesC. The influence of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the beta -elimination reaction is also discussed.