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Understanding the Reactivity of Group 6 Metal (M = Cr, W) Alkynyl Fischer Carbene Complexes with Multi‐Reactive Masked Dienes
Author(s) -
Collado Alba,
GómezGallego Mar,
Santiago Alicia,
Sierra Miguel A.
Publication year - 2019
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/ejoc.201800453
Subject(s) - chemistry , carbene , reactivity (psychology) , electrophile , nucleophile , anthrone , medicinal chemistry , denticity , adduct , reactive intermediate , metal , catalysis , organic chemistry , medicine , alternative medicine , pathology
Group 6 alkynyl Fischer carbene complexes behave as electrophiles with highly reactive masked dienes such as anthrone and 3‐hydroxy‐2‐pyrone, which also can react as bidentate nucleophiles. Both Cr 0 and W 0 alkynyl carbene complexes require tertiary amines to promote the formation of 1,4‐ C ‐addition products, but a marked dependence of the reactivity on the metal was observed. Although W 0 complexes form exclusively the 1,4‐ C ‐adducts in the presence of a catalytic amount of base, Cr 0 complexes lead to new anthrone‐derived bis‐carbene complexes, obtained by a sequential 1,4‐ C ‐ and 1,4‐ O ‐addition process with high diastereoselectivity and only in the presence of an excess of base. DFT computational studies show that the gap between the LUMO of the complex and the HOMO of the anthrone determines the differences in reactivity and that the stability of the intermediate metal allenyls formed after the initial 1,4‐addition is decisive for the outcome of the reaction.