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Angewandte Chemie International Edition
COMMUNICATION
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Scheme 1. Plausible mechanism for gold-enolate enabled mannich reaction
hydroxy-1-ynes 4, their nitrone oxidations delivered α-alkoxy
enolates that reacted preferably with imines with syn-selectivity.
In the case of aryloxyethynes, their resulting α-aryl enolates
reacted selectively with
a second nitrone to afford 3-
benzylidenebenzofuran-2-one derivatives. Herein, a change of
the chemoselectivity of the Mannich reactions is attributed to two
distinct hydrogen bonds,[17] O-H--N versus C-H--O; cooperative
catalysis is thus ascertained. The use of alkynes as the
surrogates of α-alkoxy and α-aryl enolates highlights the
significance of this work.
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We thank the Ministry of Education (MOE 106N506CE1) and the
Ministry of Science and Technology (MOST 107-3017-F-007-
002), Taiwan, for financial support of this work.
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Liu, J. Am. Chem. Soc. 2011, 133, 15372-15375.
Keywords: alkynes • nitrones • oxidative Mannich reactions •
oxidative cycloalkenations • enolates
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Cambridge Crystallographic Data Center; 3a, CCDC 1844715; 5a,
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