alpha- and beta-hydrogen eliminations in the reactions of some 3-O-triflylglycosides with (BuOK)-Bu-t and pyridine

Previous papers [10-12] reported new reactions that occur when some carbohydrate triflates are treated with MeLi (or BuLi) in Et2O to give the C-methyl(butyl) or unsaturated compounds through elimination of the CH-hydrogen bearing a CF3SO3 group ( alpha-elimination) as a proton. This paper extends the previous work and describes the reactions for some 3-O-triflyl-D-gluco- and -allo-furanosides and -pyranosides with (BuOK)-Bu-t and pyridine [instead of Me(Bu)Li], utilizing the corresponding 2- and 3-deuterated analogs. II was found that, when (BuOK)-Bu-t was used, the 3-O-triflyl-D-glucopyranosides gave 2,3- and 3,4-unsaturated compounds through alpha-hydrogen elimination (alpha-elimination) followed by (possibly) C-3 carbene formation, while the 3-O-triflyl-D-allopyranosides gave mainly 2,3-unsaturated compounds through alpha-elimination. When pyridine was used, most of the compounds gave the corresponding 3-pyridinium derivatives through an SN2 process. (C) 1997 Elsevier Science Ltd.