Synthesis 2022; 54(10): 2494-2510
DOI: 10.1055/s-0040-1719882
paper

Significant Broadening of the Substrate Scope for the Hydrated Imidazoline Ring Expansion (HIRE) via the Use of Lithium Hexamethyldisilazide

Sergey Grintsevich
a   Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii prospect, Peterhof, Saint Petersburg, 198504, Russian Federation   URL: http://krasavin-group.org
,
Alexander Sapegin
a   Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii prospect, Peterhof, Saint Petersburg, 198504, Russian Federation   URL: http://krasavin-group.org
,
a   Institute of Chemistry, Saint Petersburg State University, 26 Universitetskii prospect, Peterhof, Saint Petersburg, 198504, Russian Federation   URL: http://krasavin-group.org
b   Immanuel Kant Baltic Federal University, 14 A. Nevskogo ul., Kaliningrad, 236016, Russian Federation
› Institutsangaben

This research was supported by the Russian Science Foundation (Grant no. 19-75-30008).


Abstract

Substrates that are insufficiently activated towards the hydrated imidazoline ring expansion (HIRE) process have been previously found to deliver exclusively the products of aminoalkyl side-chain ring expansion. Attempted reversal of the process by thermal activation towards HIRE failed. We have found that for such problematic substrates the HIRE-type ring expansion can be effectively achieved by applying lithium hexamethyldisilazide (LHMDS) in toluene. LHMDS is thought to promote intramolecular transamidation, which leads to ring-expanded 10- and 11-membered heterocyclic products in modest to good yields. The process significantly broadens the substrate scope amenable to the HIRE strategy.

Supporting Information



Publikationsverlauf

Eingereicht: 26. November 2021

Angenommen nach Revision: 16. Dezember 2021

Artikel online veröffentlicht:
10. Februar 2022

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