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Alkyne Migration in Alkylidene Carbenoid Species: A New Method of Polyyne Synthesis
Author(s) -
Eisler Sara,
Chahal Navjot,
McDonald Robert,
Tykwinski Rik R.
Publication year - 2003
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.200204584
Subject(s) - carbenoid , alkyne , moiety , carbene , chemistry , conjugated system , halogen , combinatorial chemistry , aryl , catalysis , stereochemistry , organic chemistry , alkyl , polymer , rhodium
The synthesis of conjugated polyyne structures via a modification of the Fritsch–Buttenberg–Wiechell (FBW) rearrangement is reported. Our adaptation provides for the 1,2‐migration of an alkyne in a carbene/carbenoid intermediate that is conveniently effected via lithium–halogen exchange with the appropriate dibromo‐olefinic precursor. This rearrangement is quite rapidly accomplished under mild conditions (hexane solution, −78 °C), and the seemingly high migratory aptitude of the alkynyl moiety provides for efficient rearrangement. This, in turn, allows for multiple rearrangements in a single molecule, greatly facilitating the construction of highly unsaturated substrates. This procedure is exploited for the rapid synthesis of symmetrical and unsymmetrical 1,3,5‐hexatriynes, extended polyynes, and aryl polyyne building blocks. Most significantly, many of these structures have been or would be difficult to access via more traditional transition metal catalyzed homo‐ or cross‐coupling techniques.