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A New General Synthesis of 2,2‐Dialkyl‐2,3‐dihydro‐4 H ‐pyran‐4‐ones and Their Application for the in situ Preparation of Electron‐Rich Dienes in Carbonyl‐Alkyne Exchange Reactions with Acetylenes
Author(s) -
Obrecht Daniel
Publication year - 1991
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19910740106
Subject(s) - chemistry , pyran , in situ , combinatorial chemistry , medicinal chemistry , stereochemistry , organic chemistry , computational chemistry
The substituted 2,2‐dialkyl‐2,3‐dihydro‐4 H ‐pyran‐4‐ones of type II and III have been prepared by acid‐catalyzed cyclization of the corresponding substituted acetylenic ketones I in good to excellent yields ( Scheme 1 ). These 2,2‐dialkyl‐2,3‐dihydro‐4 H ‐pyran‐4‐ones II and III have been used for the in situ preparation of highly reactive dienes of type IV – VI ( Scheme 2 ) in carbonyl‐alkyne exchange reactions with electron‐poor alkynes VII to yield the highly substituted aromatic compounds VIII and IX. These reactions proceed in good yields and with excellent degree of regioselectivity. Aryl‐substituted 2,2‐dialkyl‐2,3‐dihydro‐4 H ‐pyran‐4‐ones III (R 1 = Ar) subsequently yield highly substituted biaryls. Reaction mechanisms are presented for the formation of the 2,2‐dialkyl‐2,3‐dihydro‐4 H ‐pyran‐4‐ones as well as for the carbonyl‐alkyne exchange reactions with electron‐poor acetylenes.