Elsevier

Tetrahedron

Volume 56, Issue 7, 11 February 2000, Pages 1013-1023
Tetrahedron

A New Approach to Dihydrobenzofurans and Dihydrobenzopyrans (Chromans) Based on the Intramolecular Trapping by Alcohols of Benzynes Generated from 7-Substituted-1-aminobenzotriazoles

https://doi.org/10.1016/S0040-4020(00)00021-1Get rights and content

Abstract

1-Aminobenzotriazoles 9 having 7-hydroxyalkyl substituents are efficiently converted into the corresponding benzynes 4 when treated with N-iodosuccinimide which then undergo highly efficient intramolecular trapping by the pendant hydroxyl groups leading to dihydrobenzofurans 2426 and dihydrobenzopyrans (chromans) 27, with incorporation of a synthetically useful iodine atom adjacent to the new ether bond, which allows subsequent and high-yielding homologations using Stille, Sonogashira and Heck couplings.

Section snippets

General details

Optical rotations were measured using an Optical Activity AA-10 polarimeter. Infrared spectra were obtained using a Perkin–Elmer 1720 FTIR spectrometer using liquid films on sodium chloride plates or, if solids, chloroform solutions. 1H NMR spectra were obtained using a Perkin–Elmer R32a instrument operating at 90 MHz (90) or a Bruker WM-250 instrument operating at 250 MHz. 13C NMR spectra were determined using a JEOL EX270 spectrometer operating at 67.8 MHz or the Bruker AM-400 instrument

Acknowledgements

We are most grateful to Dr Robert G. Giles (SB, Tonbridge) for helpful advice, to the EPSRC Mass Spectrometry Centre, University of Wales, Swansea, for the provision of some of the HRMS data and to SB Pharmaceuticals and the EPSRC for financial support through the CASE Scheme.

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