Organocatalytic asymmetric synthesis of dihydrocarbazoles via a formal [4+2] cycloaddition of in situ generated o-quinodimethanes with enals

An organocatalytic asymmetric [4+2] eliminative enemalononitriles with alpha,beta-unsaturated aldehydes intermediates has been developed. This approach carbazole-3-carbaldehydes, as well as its analogous in good yields and with high enantioselectivities. cycloaddition reaction of 2-methyl-indolyl methyl via in situ generated indole-ortho-quinodimethane provides straightforward access to 2,9-dihydro-1H-dihydrodibenzofuran and dihydrodibenzothiophene (C) 2016 Elsevier Ltd. All rights reserved.