850255-69-5Relevant academic research and scientific papers
Generation of α-phosphonovinyl radicals and development of a new route to highly functionalized vinylphosphonates and vinylphosphonate- incorporated carbocyclic or heterocyclic compounds via a radical trapping sequence
Ageno, Takafumi,Okauchi, Tatsuo,Minami, Toru,Ishida, Masaru
, p. 924 - 931 (2005)
The first direct generation of synthetically useful α-phosphonovinyl radicals was achieved by treatment of α-phosphonovinyl halides with a tributyltin radical. The α-phosphonovinyl radicals 2a-d were trapped with electron-rich olefins and an electron-deficient olefin to produce α-functionalized vinylphosphonates 3a-f in 16-55% yields. The α-phosphonovinyl radicals 7e-g containing the YCH2CH=CH 2 (Y = O, CH2, S) substituent at the β-position afforded mixtures of 5-exo and 6-endo cyclization products, 5e-g and 6e-g, in good yields. The 5-exo/6-endo product ratios increase in the following order of the β-substituent: OCH2CH=CH2 > CH 2CH2CH=CH2 > SCH2CH=CH 2. The effects of the β-substituents upon the cyclization reaction were discussed. Radical cyclization of α-phosphonovinyl radicals bearing functional groups such as geranyloxy, geranylthio, and (2-cyclohexen-l-yl)thio groups at the β-position afforded 5-exo, 5-exo and 6-endo, and cis-fused-5,6-ring cyclization products incorporating an α,β-unsaturated phosphonate unit within the ring, respectively, in good yields. The β-phosphonovinyl radical 20 underwent tandem radical cyclization-radical cyclization to produce a mixture of two isomeric bicyclo[4.3.0]nonenes including a vinylphosphonate moiety in high yield. The Royal Society of Chemistry 2005.
