Diastereoselective synthesis of 1-allyl and 1,2-bis(allyl)-1,2-diols: Versatile synthons for substituted tetrahydrofuran derivatives

Hydroxy ketones and 2-ketoaldehydes undergo indium mediated highly diastereoselective mono and bis-allylation reactions to give respective 1-allyl 2a-c and 1,2-bis (allyl)- 7a-c 1,2 diols. 2a undergoes I-2 / NaHCO3 and m-CPBA mediated diastereoselective intramolecular cyclizations to provide respective (2S*, 3R*. 5S*)-2,3-diphenyl-4-hydroxy-5-iodo methyltetrahydrofuran 4a and (2S*, 3R*, 5R*)-2,3-diphenyl-4-hydroxy-5-hydroxymethyl tetrahydrofuran 5b as major product.