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An Efficient Synthesis of Bicyclo[3.3.0]oct‐2‐en‐4‐ones and 2‐Azabicyclo[3.3.0]oct‐7‐en‐6‐ones via β‐Amino‐Substituted α,β‐Unsaturated Fischer Carbene Complexes
Author(s) -
Schirmer Heiko,
Funke Frank J.,
Müller Stephan,
Noltemeyer Mathias,
Flynn Bernard L.,
de Meijere Armin
Publication year - 1999
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/(sici)1099-0690(199909)1999:9<2025::aid-ejoc2025>3.0.co;2-a
Subject(s) - chemistry , substituent , bicyclic molecule , moiety , aldol reaction , aldehyde , ketone , cycloaddition , intramolecular force , acetal , stereochemistry , intramolecular reaction , enol ether , michael reaction , carbene , medicinal chemistry , ether , amine gas treating , ketene , organic chemistry , catalysis
The formal [3+2] cycloaddition of β‐amino‐substituted α,β‐unsaturated Fischer carbenechromium complexes 2 , which are easily prepared in a one‐pot procedure from terminal alkynes 1 via an initially formed alkynylidene complex by a Michael‐type addition of a secondary amine, with a variety of alkynes 3 afford the 1,2,5‐trisubstituted 3‐alkoxy‐5‐dialkylamino‐1,3‐cyclopentadienes 4 with an acetal‐protected aldehyde or ketone carbonyl group in either the 5‐substituent R 1 or the N ‐substituent R 2 . Under acidic conditions, both the enol ether moiety in the 5‐membered ring as well as the acetals in the side chains are hydrolyzed, and the resulting cyclopentenones 6 with carbonyl‐group containing side‐chains undergo facile intramolecular aldol reactions to give bicyclo[3.3.0]oct‐2‐en‐4‐ones 8 and 8‐azabicyclo[3.3.0]oct‐2‐en‐4‐ones 12 , respectively, in good to very good yields for most cases.