TY - JOUR
T1 - Thermal ring contraction of dibenz[b,f]azepin-5-yl radicals: New routes to pyrrolo[3,2,1-jk]carbazoles
AU - Crawford, Lynne A.
AU - McNab, Hamish
AU - Mount, Andrew R.
AU - Wharton, Stuart I.
PY - 2008/9/5
Y1 - 2008/9/5
N2 - Flash vacuum pyrolysis (FVP) of N-allyl- or N-benzyldibenz[b,f]azepine at temperatures from 750 to 950 degrees C gives pyrrolo[3,2,1-jk]carbazole as the major product. The mechanism of the ring contraction involves dibenzazepin-1-yl radical formation, followed by transannular attack and formation of a 2-(indol-1-yl)phenyl radical which cyclizes. The mechanism is supported by independent generation of 2-(indol-1-yl)phenyl radicals by two different methods, and the use of 1-(2-nitrophenyl)indole as a radical generator gives an optimized synthetic route to pyrrolo[3,2,1-jk] carbazole (54% overall yield in two steps from indole). The first substituted pyrrolo[3,2,1-jk]carbazoles have been synthesized by FVP methods and also by reactions of the parent compound with electrophiles, leading to a range of 4-substituted pyrrolocarbazoles.
AB - Flash vacuum pyrolysis (FVP) of N-allyl- or N-benzyldibenz[b,f]azepine at temperatures from 750 to 950 degrees C gives pyrrolo[3,2,1-jk]carbazole as the major product. The mechanism of the ring contraction involves dibenzazepin-1-yl radical formation, followed by transannular attack and formation of a 2-(indol-1-yl)phenyl radical which cyclizes. The mechanism is supported by independent generation of 2-(indol-1-yl)phenyl radicals by two different methods, and the use of 1-(2-nitrophenyl)indole as a radical generator gives an optimized synthetic route to pyrrolo[3,2,1-jk] carbazole (54% overall yield in two steps from indole). The first substituted pyrrolo[3,2,1-jk]carbazoles have been synthesized by FVP methods and also by reactions of the parent compound with electrophiles, leading to a range of 4-substituted pyrrolocarbazoles.
UR - http://www.scopus.com/inward/record.url?scp=51549089354&partnerID=8YFLogxK
U2 - 10.1021/jo800637u
DO - 10.1021/jo800637u
M3 - Article
SN - 0022-3263
VL - 73
SP - 6642
EP - 6646
JO - The Journal of Organic Chemistry (JOC)
JF - The Journal of Organic Chemistry (JOC)
IS - 17
ER -