New Insights in Frustrated Lewis Pair Chemistry with Azides.

Authors :: Boom DHA
Jupp AR
Nieger M
Ehlers AW
Slootweg JC
Source :: Chemistry (Weinheim an der Bergstrasse, Germany) [Chemistry] 2019 Oct 17; Vol. 25 (58), pp. 13299-13308. Date of Electronic Publication: 2019 Sep 09.
Publication Year :: 2019
Abstract: The geminal frustrated Lewis pair (FLP) tBu <subscript>2</subscript> PCH <subscript>2</subscript> BPh <subscript>2</subscript> (1) reacts with phenyl-, mesityl-, and tert-butyl azide affording, respectively, six, five, and four-membered rings as isolable products. DFT calculations revealed that the formation of all products proceeds via the six-membered ring structure, which is thermally stable with an N-phenyl group, but rearranges when sterically more encumbered Mes-N <subscript>3</subscript> and tBu-N <subscript>3</subscript> are used. The reaction of 1 with Me <subscript>3</subscript> Si-N <subscript>3</subscript> is believed to follow the same course, yet subsequent N <subscript>2</subscript> elimination occurs to afford a four-membered heterocycle (5), which can be considered as a formal FLP-trimethylsilylnitrene adduct. Compound 5 reacts with hydrochloric acid or tetramethylammonium fluoride and showed frustrated Lewis pair reactivity towards phenylisocyanate.<br /> (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)