1‐3‐Dipolar Cycloadditions of Trimethylsilyldiazomethane Revisited: Steric Demand of the Dipolarophile and the Influence on Product Distribution.

Abstract

It is found that the stereoselectivity concerning the cycloaddition of TmsCHN2 with dipolarophiles and the outcome of subsequent alkylations strongly depends on the steric demand of the dipolarophile. The reaction with acrylates and crotonates leads to pyrazoline esters of type (IV)/(VII) and (V)/(VIII), while starting from cinnamates regioisomeric pyrazolines like (X) are also obtained. The ratio of the latter can be enhanced by increasing temperature. -(SIMOVIC, D.; DI, M.; MARKS, V.; CHATFIELD, D. C.; REIN*, K. S.; J. Org. Chem. 72 (2007) 2, 650-653; Dep. Chem., Fla. Int. Univ., Miami, FL 33199, USA; Eng.) -Jannicke 21-105