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Gold Catalysis: 1,3‐Oxazines by Cyclisation of Allene Amides
Author(s) -
Hashmi A. Stephen K.,
Schuster Andreas M.,
Litters Sebastian,
Rominger Frank,
Pernpointner Markus
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201100132
Subject(s) - hydroamination , allene , chemistry , catalysis , steric effects , intramolecular force , oxazines , catalytic cycle , medicinal chemistry , stereochemistry , photochemistry , organic chemistry
A series of allene amides was prepared and their gold‐catalysed cyclisation was investigated. The formation of six‐membered rings, 1,3‐oxazines, was observed. Dihydropyrroles originating from intramolecular hydroamination of the distal CC double bonds of the allenes were minor side products. Mechanistic studies by in situ 31 P NMR spectroscopy showed only one additional species during the conversion in each case; a computational study of the different allyl gold(I) species involved allowed this to be assigned as the σ‐allyl gold species bearing the gold catalyst at the sterically less hindered methylene end. The regiospecific deuterodeauration of this intermediate confirmed a S E ′‐type mechanism for this last step of the catalytic cycle.