Two approaches to diverting the course of a free-radical cyclization: application of cyclopropylcarbinyl radical fragmentations and allenes as radical acceptors.
Free radical cyclization of 4 and 7 gave the expected cyclization-reduction products (5 and 8) along with considerable amounts of products derived from a cyclization-atom transfer-secondary cyclization process (6 and 9). Two approaches to avoiding these unexpected products were explored. Use of a cyclopropylcarbinyl fragmentation avoided the secondary cyclization reaction (25 or 43 --> 26 or 44), whereas use of an allene as a radical acceptor avoided the atom-transfer reaction altogether (49 --> 52).
Yang
Dexi
D
Department of Chemistry, The Ohio State University 100 West 18th Avenue, Columbus, Ohio 43210, USA.
Cwynar
Valerie
V
Donahue
Matthew G
MG
Hart
David J
DJ
Mbogo
Grace
G
D000473:Alkanes / Q000737:chemistry*; D003500:Cyclization; D003521:Cyclopropanes / Q000138:chemical synthesis* / Q000737:chemistry; D005609:Free Radicals / Q000138:chemical synthesis / Q000737:chemistry; D008968:Molecular Conformation; D013237:Stereoisomerism
D000473:Alkanes; D003521:Cyclopropanes; D005609:Free Radicals