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Efficient syntheses of thiochromans via cationic cycloadditions
1Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, 32611-7200, USA. katrizky@chem.ufl.edu
The Journal of Organic Chemistry
|August 4, 2001
Abstract:
alpha-(Benzotriazolyl)methyl thioethers 1a-e reacted with styrenes under Lewis acid catalysis to give novel polysubstituted thiochromans (3,4-dihydro-2H-1-benzothiopyrans) 3-14 and 16-20 in generally high yields. Most thiochromans were isolated as one diastereomer following recrystallization. The configuration and conformation of the products are predicted on the basis of their NMR data. A stepwise reaction, proceeding via a [4(+) + 2] cationic polar cycloaddition mechanism, is proposed.