Lithiation of 2-chloroglucal derivatives provides ready access to the corresponding 1-lithioglucals which undergo a variety of serve useful intermediates for further elaboration of the carbohydrate nucleus. Removal of the 2-chloro substituent may be affected using a Birch-type reduction. (c) 2006 Elsevier Ltd. All rights reserved.
Second generation benzannulation reactions: Sugar-derived Fischer chlorocarbene complexes in organic synthesis
作者:Michael.R. Hallett、James E. Painter、Peter Quayle、Dean Ricketts、Prakash Patel
DOI:10.1016/s0040-4039(98)00315-3
日期:1998.4
The facile metallation of 2-chloroglucal derivatives 8 and 11 affords ready access to the corresponding Fischer carbene complexes 10 and 13. Carbene complexes 10 and 13 undergo benzannulationreactions with acetylenes to provide functionalised benzopyrans in moderate overall yields.
Highly diastereoselective 1,2-dichlorination of glycals using NCS/PPh3: study of substituent and solvent effects
作者:Altaf Hussain、Debaraj Mukherjee
DOI:10.1016/j.tet.2013.12.088
日期:2014.2
Highly diastereoselective 1,2-dichlorination of glycals has been achieved at room temperature conditions in good to excellent yields using a milder, more convenient, less hazardous reagent combination NCS/ PPh3 giving only one major product out of four possible diastereomers [either alpha-gluco (2) or alpha-manno (4)] depending upon the substituents. The diastereoselectivity is maximum (100% alpha/beta-selectivity as well as cis/trans selectivity) for D-galactal and L-rhamnal derivatives. Detailed studies showed that solvent and substituent effects play a significant role in determining the product distribution. (C) 2014 Elsevier Ltd. All rights reserved.