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DOI: 10.1055/s-2005-918482
Diastereoselective Friedel-Crafts Cyclization Reactions to 2-Substituted 1-Phenyl-1,2,3,4-tetrahydronaphthalenes
Publication History
Received
15 September 2005
Publication Date:
14 November 2005 (online)


Abstract
1′-Substituted 1-phenyl-1-(3′-phenylprop-1′-yl)alkenes, 1-substituted 2-methyl-4-phenylbutanols, and 2,5-diphenyl-3-methyl-2-pentanol were synthesized from known starting materials. These compounds and the known epoxide 2-phenethyl-3-phenyloxirane were subjected to Brønsted or Lewis acid promoted Friedel-Crafts cycloalkylations, which proceeded with almost perfect diastereoselectivity (dr >95:5). For the cyclization reaction to tetralins (five examples) trifluoromethane sulfonic acid proved to be the reagent of choice (91-98% yield). The diastereoselective cyclization of epoxide 2-phenethyl-3-phenyloxirane to trans-1,2,3,4-tetrahydro-1-phenylnaphth-2-ol was accompanied by side reactions and the yield was lower (45%). The reactions occurred stereoconvergently, i.e. a mixture of diastereoisomers led to a single diastereomeric product under kinetic control. An explanantion for the observed diastereoselectivity is put forward.
Key words
carbocations - stereoselective synthesis - electrophilic aromatic substitutions - alkylations - regioselectivity