Two efficient procedures involving tin hydride or thiophenol-mediated intramolecular homolytic substitution at the sulfur atom are reported. They lead to the generation of varied P(V)-centered radicals from the corresponding aryl or alkyne thiophosphorus substrates. The radical formed can be trapped by an olefin via an intermolecular addition, leading to the construction of C–P bonds. Thiophosphination
Radical Cyclizations of Alkenyl Acylphosphonate Derivatives under Thermal and Photochemical Conditions
作者:Chang Ho Cho、Sunggak Kim、Motoki Yamane、Hironori Miyauchi、Koichi Narasaka
DOI:10.1246/bcsj.78.1665
日期:2005.9
The use of alkenyl acylphosphonate and acylphosphine oxide derivatives as acceptors in radical cyclizations was studied under thermal and photochemical conditions, respectively. The cyclizations of alkenyl acylphosphonates under thermal conditions occurred smoothly in refluxing dioxane using benzoyl peroxide as an initiator; the addition of diethyl phosphite increased the chemical yield. Photochemically induced cyclizations of alkenyl acyldiphenylphosphine oxides at 300 nm gave similar results, although a notable difference was observed in one case. The intramolecular cyclization of S-but-3-enyl phosphinothiolformates occurred under thermal and photochemical conditions, providing thiolactones, whereas S-pent-4-enyl phosphinothiolformate afforded the tetrahydrothiophene derivative under similar conditions.
BCl3 as the sole boron source, the boryl group and thiol group are added to the C-C double bonds simultaneously. After hydrolysis, the corresponding ((tetrahydrothiophen-2-yl)methyl)boronic acid, ((tetrahydro-2H-thiopyran-2-yl)methyl)boronic acid, ((2,3-dihydrobenzo[b]thiophen-2-yl)methyl)boronic acid and (thiomorpholin-2-ylmethyl)boronic acid are obtained with good yield. The boronic acids obtained
1,3-Rearrangement of allylic sulphones: Rearrangement-cyclisation of allylic 4-pentenyl sulphones
作者:Eifion D. Phillips、Gordon H. Whitham
DOI:10.1016/s0040-4039(00)60462-8
日期:1993.4
Allylic alkyl sulphones CH2:CHC(Me)2SO2R (RMe, Et, iPr, tBu, CH2SiMe3, CH2CH2SiMe3, and CH2CH(OH)Me underwent 1,3-rearrangement on treatment with benzoyl peroxide in tBuOH. 1,3-Rearrangement did not occur in cases (RCH2Ph, CH2COMe) where the intermediate sulphonyl radical RSO2· could undergo loss of sulphur dioxide to form a resonance-stabilised alkyl radical. Allylic 4-pentenyl sulphones undergo