Radical addition reactions of fluorinated species. Part 7. Highly selective two-step synthesis of 1-(polyfluoroalkyl)ethane-1,2-diols; regioselectivity of the additions of methylated 1,3-dioxolanes to perfluoroolefins
摘要:
The two-step synthesis of the diols is based on the radical addition of 2,2-dimethyl-1,3-dioxolane (1), a protected ethane-1,2-diol, to perfluoroalk-1-enes R-F-CF=CF2 (RF=CF3, C9F19; 2, 3) and perfluoro[trifluorovinyl (poly)ethers] RFO-CF=CF2 (R-F=C3F7, C3F7O[CF(CF3)CF2], CF3(OCF2CF2)(4); 4-6) with preparative yields above 90% in each step. The additions were initiated photochemically or by dibenzoyl peroxide and were completely chemoselective and almost completely regioselective. 4-Fluoroalkylated dioxolanes obtained (7-11) were deprotected by acid methanolysis to afford 1-polyfluoroalkylethane-1,2-diols (12-16). 1,3-Dioxolane (27) or 2,2,4-trimethyl-1, 3-dioxolane (30) reacted at two centers to yield regioisomeric mixtures of fluoroalkylated dioxolanes. The factors influencing fluoroolefin and dioxolane regioselectivity are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.
Radical addition reactions of fluorinated species. Part 7. Highly selective two-step synthesis of 1-(polyfluoroalkyl)ethane-1,2-diols; regioselectivity of the additions of methylated 1,3-dioxolanes to perfluoroolefins
摘要:
The two-step synthesis of the diols is based on the radical addition of 2,2-dimethyl-1,3-dioxolane (1), a protected ethane-1,2-diol, to perfluoroalk-1-enes R-F-CF=CF2 (RF=CF3, C9F19; 2, 3) and perfluoro[trifluorovinyl (poly)ethers] RFO-CF=CF2 (R-F=C3F7, C3F7O[CF(CF3)CF2], CF3(OCF2CF2)(4); 4-6) with preparative yields above 90% in each step. The additions were initiated photochemically or by dibenzoyl peroxide and were completely chemoselective and almost completely regioselective. 4-Fluoroalkylated dioxolanes obtained (7-11) were deprotected by acid methanolysis to afford 1-polyfluoroalkylethane-1,2-diols (12-16). 1,3-Dioxolane (27) or 2,2,4-trimethyl-1, 3-dioxolane (30) reacted at two centers to yield regioisomeric mixtures of fluoroalkylated dioxolanes. The factors influencing fluoroolefin and dioxolane regioselectivity are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.