Cycloaddition of homochiral dihydroimidazoles: a 1,3-dipolar cycloaddition route to optically active pyrrolo[1,2-a]imidazoles.
N-Alkylation of optically active 1-benzyl-4-phenyl-4,5-dihydroimidazole with active alkyl halides and treatment of the so-formed 4,5-dihydroimidazolium ions with DBU in the presence of a range of electron-deficient alkene dipolarophiles, constitutes a 'one-pot' cascade terminating in a 1,3-dipolar cycloaddition reaction that affords optically active pyrrolo[1,2-a]imidazoles. Three bonds of the so-formed pyrrolidine moiety are constructed in this cascade. The cycloaddition follows an endo approach of dipole and dipolarophile with anti geometry of the dipole and facial selectivity derived from the phenyl substituent. Inter- and intramolecular cycloaddition modes are observed.
Department of Chemistry, Loughborough University, Loughborough, Leics, UK LE11 3TU. r.c.f.jones@lboro.ac.uk
Raymond C F
RC
Jones
Kevin J
KJ
Howard
John S
JS
Snaith
Alexander J
AJ
Blake
Wang-Shei
WS
Li
Peter J
PJ
Steel
D018360:Crystallography, X-Ray; D003500:Cyclization; D007093:Imidazoles / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D011758:Pyrroles / Q000737:chemistry*; D013237:Stereoisomerism
D007093:Imidazoles; D011758:Pyrroles