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Double Insertion of Alkynes into Chromium‐Carbon Bonds of β‐Donor‐Substituted Vinylcarbene Complexes of Chromium—A Simple Route to Cyclopenta[ b ]pyrans
Author(s) -
Stein Frank,
Duetsch Michael,
Lackmann Rolf,
Noltemeyer Mathias,
de Meijere Armin
Publication year - 1991
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199116581
Subject(s) - chromium , planarity testing , yield (engineering) , chemistry , stereochemistry , crystallography , organic chemistry , materials science , metallurgy
Only products with severely restricted substitution patterns could be produced, and in low yields, by the multistep syntheses previously known for the pseudoazulenes. In contrast, the easily obtained vinylcarbenechromium complex 1 described here offers a simple high‐yield access to the cyclopenta[ b ]pyranes 2 when a quaternary group occupies the β‐position. The X‐ray structural analysis shows that the rings of the heterobicycle 2 deviate from planarity by a mere 3.7 o .