Toggle Main Menu Toggle Search

Open Access padlockePrints

Synthesis of highly hindered oxepins and an azepine from bis-trityl carbenium ions: structural characterisation by NMR and X-ray crystallography

Lookup NU author(s): Dr Kieren Carey, Emeritus Professor Bill Clegg, Dr Mark Elsegood, Professor Bernard Golding, Dr Maurice Hill

Downloads

Full text for this publication is not currently held within this repository. Alternative links are provided below where available.


Abstract

Reactions of the bis-carbenium ion 2,2'-bis[bis(p-methoxyphenyl)methyl]biphenyl ditetrafluoroborate with ammonia, n-propylamine and benzylamine have been studied with the aim of developing an acid-labile protecting group for primary amines that masks both hydrogen atoms of the NH2 group. Although the parent 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]azepine was isolated and fully characterised, the corresponding azepines could not be obtained in a pure state from the reactions with the primary amines. The bis-carbenium ion was prepared from the treatment of 2,2'-bis[bis(p-methoxyphenyl) hydroxymethyl]biphenyl with fluoroboric acid. Attempts to prepare the corresponding diphenyl analogue were unsuccessful using either fluoroboric acid or boron trifluoride. The only product isolated from these reactions was 5,5,7,7-tetraphenyl-5,7-dihydrodibenzo[c,e]oxepin. The oxepin and its phenyl-p-methoxyphenyl and bis(p-methoxyphenyl) analogues were efficiently obtained by dehydration of the corresponding diol, e. g. 2,2'-bis[ bis( p-methoxyphenyl) hydroxymethyl]biphenyl, in the presence of 3 Angstrom molecular sieves or Amberlite IR-200 resin. The compounds 2,2'-bis[bis(p-methoxyphenyl)hydroxymethyl] biphenyl, (R,R/S,S)-2,2'-[bis(phenyl-p-methoxyphenyl)hydroxymethyl] biphenyl, 5,5,7,7-tetraphenyl-5,7-dihydrodibenzo[c,e]oxepin, 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]oxepin and 5,5,7,7tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e]azepine were characterised by crystal structure analyses. 2,2'-Bis[bis(p-methoxyphenyl)hydroxymethyl]biphenyl and 5,5,7,7-tetrakis(p-methoxyphenyl)-5,7-dihydrodibenzo[c,e] oxepin exhibited dynamic NMR properties, and free energy barriers have been determined.


Publication metadata

Author(s): Elsegood MRJ; Golding BT; Clegg W; Hill MNS; Carey KA; Maskill H

Publication type: Article

Publication status: Published

Journal: Journal of the Royal Chemical Society: Perkin Transactions 1

Year: 2002

Issue: 23

Pages: 2673-2679

ISSN (print): 1472-7781

ISSN (electronic): 1364-5463

Publisher: Royal Society of Chemistry

URL: http://dx.doi.org/10.1039/b207108h

DOI: 10.1039/b207108h


Altmetrics

Altmetrics provided by Altmetric


Actions

Find at Newcastle University icon    Link to this publication


Share