Unusual Reactions of (+)-Car-2-ene and (+)-Car-3-ene with Aldehydes on K10 Clay
作者:Irina V. Il'ina、Konstantin P. Volcho、Dina V. Korchagina、Georgi E. Salnikov、Alexander M. Genaev、Elena V. Karpova、Nariman F. Salakhutdinov
DOI:10.1002/hlca.201000145
日期:2010.11
The reactions of (+)‐car‐2‐ene (1) and (+)‐car‐3‐ene (2) with aldehydes in the presence of montmorillonite clay were studied for the first time (Schemes 3 and 5). The major products of these reactions are optically active, substituted hexahydroisobenzofurans, probably formed as a result of an attack of the protonated aldehyde at the cyclopropane ring. Quite unexpectedly, the products are cis‐configured
HNT clearly indicates that weak Brønsted sites favored the reaction. On the contrary, over strong Brønsted and Lewis acids (Amberlyst-15, scandium triflate), the yield of isobenzofurans did not exceed 16% with formation of mainly 2-carene isomerization products. DFT calculations showed that interactions of the aldehyde with cyclopropane moiety of 2-carene giving isobenzofurans are more beneficial than