jo901834q_si_003.pdf (293.9 kB)
Two Approaches to Diverting the Course of a Free-Radical Cyclization: Application of Cyclopropylcarbinyl Radical Fragmentations and Allenes as Radical Acceptors
journal contribution
posted on 2009-11-20, 00:00 authored by Dexi Yang, Valerie Cwynar, Matthew G. Donahue, David J. Hart, Grace MbogoFree 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).