A Concise Synthesis of
<i>rac</i>
‐
<i>Ambrox</i>
®
<i>via</i>
the Palladium(0)‐Catalyzed Carboalkoxylation of an Allylic Ammonium Salt, as Compared to a Formaldehyde Hetero
<i>Diels–Alder</i>
Approach
作者:Christian Chapuis、David Skuy、Claude‐Alain Richard
DOI:10.1002/hlca.201900097
日期:2019.7
followed by a 1.5 mol‐% Pd‐catalyzed carbomethoxylation of quaternized 31b, leads to the methyl ester 36a. This latter could also be obtained in optically pure form by carbomethoxylation of the corresponding (+)‐acetate. Final reduction‐cyclization may be conducted as earlier described, towards the desired odoriferous rac‐Ambrox® 38a, or its pure (−)‐enantiomer. Generation of a π‐allyl Pd complex from an allylic
对二乙基烯丙胺29b或30进行酸性环化,然后进行季铵化31b的1.5 mol%Pd催化的碳甲氧基化反应,生成甲酯36a。后者也可以通过相应的(+)-乙酸酯的碳甲氧基化以光学纯净的形式获得。如上所述,朝向期望有气味的最终还原的环化可以进行外消旋-艾姆罗克斯® 38A,或它的纯的( - ) -对映体。由烯丙基铵盐生成π烯丙基Pd络合物,然后进行碳烷氧基化是新颖的。从法呢烯2开始仅需五个化学步骤,目前的工作构成的最简洁的全合成外消旋-艾姆罗克斯® 38A是最新的。