Carbo-siloles, Part 2: Synthesis and Stereochemical Resolution of a Carbo-silolane Redox Equivalent.

Autor: Saccavini, Catherine, Tedeschi, Christine, Lepetit, Christine, Yahi, Leila, Pistre, Caroline, Maraval, Valérie, Chauvin, Remi
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Zdroj: Phosphorus, Sulfur & Silicon & the Related Elements; Jun2009, Vol. 184 Issue 6, p1573-1585, 13p, 6 Diagrams, 1 Chart, 1 Graph
Abstrakt: Carbo-siloles could a priori be generated by eliminative aromatization of sila[5]pericyclyne precursors with adjacent C─OR and C─H vertices. The synthesis of tetraoxy-sila[5]pericyclyne representatives (“carbo-silolanes” 2a and 2b) has been tackled through several [(15-n)+n] ring formation strategies. After having first attempted a [14+1] route from dichlorodiphenylsilane and a skipped pentayne (3), a [5+10] route proceeded successfully from diethynyldiphenylsilane (7) and a triynedial (4), to give the sila[5]pericyclynediol (2a) as a mixture of six diastereomers in 20% yield. Sequential chromatographies afforded one pure diastereomer of 2a. DFT calculations of a model dihydroxy, dimethoxy-carbo-silolane indicate an envelope conformation of the carbo-meric five-membered ring. Methylation of the two secondary carbinol vertices of 2a afforded the corresponding tetramethoxy carbo-silolane (2b) in 68% yield. Aromatization to the targeted carbo-silole by treatment with Et2O·BF3 of 2b proved awkward. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index