Enantioselective Construction of Chiral 2,3-<i>cis</i>-Dimethyldihydrobenzofuran with an All-Carbon Quaternary Center: An Efficient Approach to (+)/(−)-PI-220 and (+)-3-<i>epi</i>-Furaquinocin C
A new strategy for the enantioselective construction of chiral 2,3‐cis‐dimethyldihydrobenzofurans has been developed by a ruthenium‐catalyzed asymmetric hydrogenation of racemic α‐aryloxybutanone via dynamic kinetic resolution (DKR), combined with a palladium‐catalyzed intramolecular reductive Heck cyclization. Starting from optically active 2,3‐cis‐dimethyldihydrobenzofuran, the natural products (+)/(−)‐PI‐220
DYKAT of Baylis−Hillman Adducts: Concise Total Synthesis of Furaquinocin E
作者:Barry M. Trost、Oliver R. Thiel、Hon-Chung Tsui
DOI:10.1021/ja0277834
日期:2002.10.1
Baylis-Hillman adducts are easily accessible building blocks; the lack of asymmetric versions of the Baylis-Hillman reaction has however precluded their widespread use in asymmetric synthesis. A Pd-catalyzed DYKAT on carbonates derived from Baylis-Hillman adducts, followed by a reductive Heck reaction, allows the enantio- and diastereoselective construction of dihydrobenzofurans in a very efficient manner. These synthons represent the core structure of the furaquinocins. Introduction of different side chains and use of different squaric acid derivatives for the construction of the naphthoquinone allow the flexible synthesis of this class of natural products. This new approach is successfully applied to the synthesis of furaquinocin E and an analogue.