Issue in Honor of Prof. Charles Rees ARKIVOC 2002 (vi) 152-163
Synthesis of some new 2-heterosubstituted 4,5-dihydroimidazoles
Raymond C. F. Jones,*a James N. Iley,b and Pedro M. J. Loryb
a Department of Chemistry, Loughborough University, Loughborough, Leics. LE11 3TU, UK b Chemistry Department, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK E-mail:
[email protected]
Dedicated to Professor Charles Rees on his 75th birthday (received 07 May 02; accepted 18 Aug 02; published on the web 26 Aug 02)
Abstract
Several new 4,5-dihydroimidazoles (and the corresponding imidazolium salts) carrying heteroatom substituents at C-2 have been prepared from the corresponding tetrahydroimidazol-2ones and/or -thiones.
Keywords: 4,5-Dihydroimidazole, imidazolium salt, imidazoline
Introduction
As part of a programme to prepare optically active nitrogen heterocycles,1 we have reported on the use of 4,5-dihydroimidazolium ylides 2, available from the 4,5-dihydroimidazoles (2imidazolines) 1, in the assembly of pyrrolo[1,2-a]imidazoles (Scheme 1).2 Reductive removal of the templating atoms affords pyrrolidines.3
N N CH2Ph N N Ph CH2Ph X R Y N N Ph CH2Ph X Y R H HN X Y + – DBU i, NaBH3CN, H+XCH2Br ii, H2, Pd(OH)2 Ph
R
S-12
Scheme 1. Synthesis of optically active pyrrolidines from 4,5-dihydroimidazolium ylides.
We proposed to extend this strategy to 2-heteroatom substituted 4,5-dihydroimidazoles 3 and their quaternary salts with the expectation that the corresponding cycloadducts 4 could lead to pyrrolidones on template removal (Scheme 2). Although this strategy was ultimately not fruitful,
ISSN 1424-6376 Page 152 ©ARKAT USA, Inc
