Open Access Repository

Synthesis of some benzoxaza and benzodioxaza heterocycles: Use of the Meisenheimer rearrangement route to fused medium-ring systems

Downloads

Downloads per month over past year

Gunawardana, IWK (1982) Synthesis of some benzoxaza and benzodioxaza heterocycles: Use of the Meisenheimer rearrangement route to fused medium-ring systems. Research Master thesis, University of Tasmania.

[img]
Preview
PDF (Whole thesis)
Whole-gunawarda...pdf | Download (4MB)
Available under University of Tasmania Standard License.

Abstract

The aim of this work was to prepare examples of benzodioxazocine
and benzodioxazonine ring systems by the Meisenheimer rearrangement of
the N-oxides of related benzoxaza systems.
The 1,4-benzoxazepine and 1,5-benzoxazocine derivatives required
as starting materials were prepared by two different ring construction
methods, viz. the Bischler-Napieralski cyclization and a C-N type
condensation. For example, 8-methoxy-5-phenyl-2,3-dihydro-1,4-
benzoxazepine was obtained by the Bischler-Napieralski cyclization of
an amide precursor. Three other 1,4-benzoxazepine derivatives and
9-methoxy-6-phenyl-3,4-dihydro-2H-1,5-benzoxazocine were similarly
prepared (Chapters 2 and 3).
A C-N type ring construction method was employed to prepare
5-phenyl-2,3-dihydro-1,4-benzoxazepine and its 7-chloro analogue. In
these cases the precursors were amino-ketones.All these cyclic imines were then converted to the corresponding
N-methyl amines by quaternization and reduction. These amines were
converted to their N-oxides for use in the Meisenheimer rearrangement.
The Meisenheimer rearrangement of 1,4-benzoxazepine-N-oxides
proceeded smoothly giving rise to the corresponding 1,5,4-benzodioxazocine
derivatives in high yields. For example, 9-methoxy-4-methyl-6-phenyl-
3,4-dihydro-2H,6H-1,5,4-benzodioxazocine was prepared from 8-methoxy-
4-methyl-5-phenyl-2,3,4,5-tetrahydro-1,4-benzoxazepine-N-oxide. Five
analogous 1,5,4-benzodioxazocines were similarly prepared (Chapter 4).
However, when the 1,5-benzoxazocine-N-oxide derivative was subjected
to this rearrangement at about 10°, only decomposition products,
including hydroxylamines, were obtained. At lower temperatures (-5°-0°)
the Meisenheimer rearrangement of this N-oxide gave the expected ring
enlarged product, 10-methoxy-5-methyl-7-phenyl-2,3,4,5-tetrahydro-7// 1,6,5-benzodioxazonine in 50% yield. The 1,5,4-benzodioxazocine and
1,6,5-benzodioxazonine ring systems have not been described previously.

Item Type: Thesis (Research Master)
Additional Information:

Copyright the Author-The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s)

Date Deposited: 08 Oct 2014 23:32
Last Modified: 15 Sep 2017 01:06
Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page
TOP