Chan Audrey, Scheidt Karl A
Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
J Am Chem Soc. 2008 Mar 5;130(9):2740-1. doi: 10.1021/ja711130p. Epub 2008 Feb 9.
N-Heterocyclic carbenes derived from N-mesityl-N-methyltriazolium salts are effective catalysts for generating homoenolate species from alpha,beta-unsaturated aldehydes. The unique intermediate adds to the electrophilic nitrogen of 1-acyl-2-aryldiazenes, and the resulting activated carbonyl unit undergoes an intramolecular acylation event. This formal [3+2] cycloaddition between alpha,beta-unsaturated aldehydes and acylaryldiazenes, catalyzed by an N-heterocyclic carbene, produces substituted pyrazolidinones in good yields. This new NHC-catalyzed reaction accommodates aromatic and alkyl alpha,beta-unsaturated aldehydes and various aromatic diazenes. A chiral triazolium salt catalyzes the formation of the pyrazolidinone product in moderate yield and good enantioselectivity. The pyrazolidinones can undergo reductive N-N bond cleavage to give beta-amino acid derivatives.
源自N-均三甲苯基-N-甲基三唑鎓盐的N-杂环卡宾是从α,β-不饱和醛生成同烯醇化物物种的有效催化剂。这种独特的中间体加成到1-酰基-2-芳基重氮的亲电氮上，并且生成的活化羰基单元发生分子内酰化反应。这种由N-杂环卡宾催化的α,β-不饱和醛与酰基芳基重氮之间的形式上的[3+2]环加成反应，能以良好的产率生成取代的吡唑烷酮。这种新的NHC催化反应适用于芳族和烷基α,β-不饱和醛以及各种芳族重氮。一种手性三唑鎓盐能以中等产率和良好的对映选择性催化吡唑烷酮产物的形成。吡唑烷酮可进行还原性N-N键裂解以得到β-氨基酸衍生物。
