Kocovsky,P.; Cerny,V., Collection of Czechoslovak Chemical Communications, 1977, vol. 42, p. 353 - 365
作者:Kocovsky,P.、Cerny,V.
DOI:——
日期:——
Tandem Carbon-Radical Peroxidation-Addition to Carbonyl Groups Reaction. A New Synthesis of Steroidal .beta.-Peroxy Lactones
作者:Alicia Boto、Rosendo Hernandez、Ernesto Suarez、Carmen Betancor、Maria S. Rodriguez
DOI:10.1021/jo00130a020
日期:1995.12
A mild and efficient synthesis of beta-peroxy lactones by alkoxy radical beta-fragmentation reaction of gamma-hydroxy carbonyl compounds is described. Steroidal models 5-hydroxy-4-nor-3-oxa-5 alpha-cholestan-2-one (1), 5-hydroxy-5 alpha-cholestan-2-one (2), and 5,17 beta-dihydroxy-4-nor-5 alpha-androstan-2-one 17-acetate (3) were synthesized to test the present methodology. These substrates are subjected to photolysis with visible light in the presence of (diacetoxyiodo)benzene, lead tetraacetate, or HgO, I-2, and molecular oxygen to generate the corresponding alkoxy radical. The fragmentation of this radical results in the carbon radical which is trapped by molecular oxygen in the key step to generate a peroxy radical. Intramolecular addition of this peroxy radical to the carbonyl group present in the molecule is followed by beta-fragmentation to yield the peroxy lactone radical. Subsequent trapping of this radical results in stable peroxy lactone. In all cases, regiospecific beta-fragmentations and stereoselective peroxidation at C-10 radical were observed. This operationally simple multistep radical procedure permitted us to synthesize steroidal beta-peroxy lactones 8, 12, and 15 in moderate to good yields.
Sequential alkoxy radical fragmentation. A one-step method for breaking two 1,3-positioned CC bonds
作者:Alicia Boto、Carmen Betancor、Rosendo Hernández、Mariá S. Rodríguez、Ernesto Suárez
DOI:10.1016/s0040-4039(00)74111-6
日期:1993.7
Cyclic hydroxy-ketones (1) and (2) in the presence of (diacetoxyiodo)benzene or mercuric oxide and iodine under oxygen atmosphere and irradiation with visible light undergo a new sequential alkoxy radical fragmentation-radical peroxidation-peroxyradical cyclization-alkoxy radical fragmentation reaction. This methodology allows the cleavage of two 1,3-positioned C-C bonds in a single step and constitutes a new synthesis of beta-peroxylactones.