Regioselective Reductive Alkylation of 3,4,5-Trimethoxybenzaldehyde Dimethylacetal: A New Synthesis of 4-Alkyl-3,5-dimethoxybenzaldehydes and 2,5-Dialkyl-1,3-dimethoxybenzenes
High-Yielding Total Synthesis of Sexually Deceptive Chiloglottones and Antimicrobial Dialkylresorcinols through an Organocatalytic Reductive Coupling Reaction
作者:Rudrakshula Madhavachary、Dhevalapally B. Ramachary
DOI:10.1002/ejoc.201403128
日期:2014.11
Biologically important, less-explored natural products of sexuallydeceptivechiloglottones, antimicrobialdialkylresorcinols, and their many analogues were synthesized in very good yields in a sequential two-pot manner by using an “organocatalyticreductivecouplingreaction” as the key step.
The regioselectivity of the reductive cleavage of 3,4,5-trimethoxybenzyl methyl ether strongly depends on the alkali metal employed as a reducing agent and solvent effects. Reactions run using Na as a reducing agent led to aromatic C(4)-O bond cleavage, whilst reductions run in the presence of Na/15-crown-5, or using Li as a reducing agent, led to highly regioselective benzylic C-O bond cleavage. This regioselectivity turnaround is discussed in terms of major solvent effects affecting the fragmentation paths of a common reaction intermediate. Synthetic applications of these findings led to the synthesis of biologically active compounds, like 2,5-dialkyl-substituted resorcinols, or 1-(3,4,5-trimethoxyphenyl)-2-arylethanes structurally related to combretastatin. (C) 2007 Elsevier Ltd. All rights reserved.
KANAKAM, CHARLES C.;MANI, NEELAKANDHA S.;RAMANATHAN, HALASYA;SUBBA, RAO G+, J. CHEM. SOC. PERKIN TRANS. PT 1,(1989) N1, C. 1907-1913
作者:KANAKAM, CHARLES C.、MANI, NEELAKANDHA S.、RAMANATHAN, HALASYA、SUBBA, RAO G+