Sherborne GJ, Diène C, Kemmitt P, Smith AD. Access to a Diverse Array of Bridged Benzo[1,5]oxazocine and Benzo[1,4]diazepine Structures.
Org Lett 2023. [PMID:
37996078 DOI:
10.1021/acs.orglett.3c03392]
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Abstract
The preparation of bridged benzo[1,5]oxazocines and benzo[1,4]diazepines is demonstrated from simple aniline and aldehyde starting materials. A one-pot condensation/6π electrocyclization is followed by an intramolecular trapping of the 2,3-dihydroquinoline intermediate by nitrogen or oxygen nucleophiles to give bridged seven- and eight-membered products. Using 3-hydroxypyridinecarboxaldehydes results in a stable zwitterionic structure that can undergo a diastereoselective reduction under hydrogenative conditions. A similar cyclization/hydrogenation pathway with excellent diastereoselectivity is also demonstrated from 2-pyridyl-substituted 1,2,3,4-tetrahydroquinolines.
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