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Synthesis and Hydrolysis of [Alkenyl(alkoxy)carbene]manganese Complexes: Evidence for a Transient Allylic Intermediate on the Way to α,β‐Unsaturated Aldehydes
Author(s) -
Mongin Carole,
Ortin Yannick,
Lugan Noël,
Mathieu René
Publication year - 1999
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/(sici)1099-0682(199905)1999:5<739::aid-ejic739>3.0.co;2-i
Subject(s) - chemistry , protonation , aldehyde , carbene , medicinal chemistry , alkoxy group , allylic rearrangement , cationic polymerization , hydrolysis , acetonitrile , aldol condensation , manganese , aldol reaction , stereochemistry , organic chemistry , catalysis , ion , alkyl
A variety of alkenylcarbene complexes [Cp′(CO) 2 Mn=C(OEt)CH=CHR] ( 3 ) (Cp′ = η 5 ‐MeC 5 H 4 ) was obtained in a straightforward manner upon aldol condensation of [Cp′(CO) 2 Mn=C(OEt)CH 3 ] ( 1 ) with aromatic and α,β‐unsaturated aldehydes RC(H)O ( 2 ). The reaction is totally stereoselective, giving ( E )‐ or ( all‐E )‐alkenylcarbenes only. The protonation of 3 at low temperature followed by reaction with water affords the α,β‐unsaturated aldehyde complexes [Cp′(CO) 2 Mn(η 2 ‐RCH=CHCHO] ( 5 ), from which the aldehydes RC(H)=C(H)C(H)O ( 6 ) were displaced by acetonitrile. The intermediate aldehyde complexes are shown to result from the hydrolysis of a transient cationic π‐allyl species [Cp′(CO) 2 Mn(η 3 ‐RCHCHC(OEt)H] + ([ 4 ] + ) formed upon protonation of 3 .