A series of related 6,7-dibromoindole compounds were prepared to study the effects of pyrrole and benzene ring substitution patterns on the regioselectivity of 6,7-indole aryne cycloadditions with 2-tert-butylfuran. The arynes were generated by our metal-halogen exchange/elimination protocol. The results of this investigation reveal that substitution at the 3-position on the indole ring in particular results in remarkable regiocontrol that favored the contrasteric products. Aromatic conjugation at this site significantly enhanced this effect. However, the presence of most 4-or 5-substituents generally resulted in markedly reduced selectivity. Exceptions in this latter series included the 4-ethyl and 4-iodo cases both of which also gave predominantly contrasteric products even in the absence of a beneficial C-3 substituent.

Substitution. -(NERURKAR, A.; CHANDRASOMA, N.; MAINA, L.; BRASSFIELD, A.; LUO, D.; BROWN, N.; BUSZEK*, K. R.; Synthesis 45 (2013) 13, 1843-1852, http://dx.doi.org/10.1055/s-0033-1338911 ; Dep. Chem., Univ. Mo., Kansas City, MO 64110, USA; Eng.) -Mais 43-111

Dimethyldioxirane (DMD) was used to synthesize heterocyclic aromatic TV-oxides enabling the product isolation and reaction solutions to be free of potentially dangerous peroxide intermediates. Additionally, this work combines important crystallographic, spectroscopic, and melting point data to shed light on inconsistent literature previously reported for the identity of 2,4'-bipyridine-W-oxide. Brought to you by | University of Arizona Authenticated Download Date | 5/26/15 4:04 PM