Triphenylsilyl as a Protecting Group in the Synthesis of 1,12-Heterodisubstituted p-Carboranes

Autor:	Piotr Kaszynski, Serhii Pakhomov, Birgit Reeves, Andrew G. Douglass, and Zbyněk Janoušek
Rok vydání:	2000
Předmět:	chemistry.chemical_classification Sulfenyl chloride Aryl Organic Chemistry Iodide Medicinal chemistry chemistry.chemical_compound chemistry Bromide Electrophile Nucleophilic substitution Organic chemistry Carborane Protecting group
Zdroj:	The Journal of Organic Chemistry. 65:1434-1441
ISSN:	1520-6904 0022-3263
Popis:	A triphenylsilyl group is used as an auxiliary in the synthesis of heterodisubstituted p-carboranes via triphenylsilyl-p-carborane (1). The preparation of 1 is statistical, but with recovery of the starting p-carborane, the effective conversion to 1 is about 90%. Carborane 1 has been easily converted to its lithium and copper derivatives, which were reacted with a range of electrophiles including alkyl halides: an aryl iodide, an acetylene bromide, and a sulfenyl chloride. The derivatives of 1 are crystalline and UV active, which facilitates their isolation and purification. The Ph(3)Si group is efficiently removed with fluoride to give monosubstituted p-carboranes I, which upon further nucleophilic substitution yield p-carboranes II. The yields of heterodisubstituted products II are higher than for direct, "statistical" syntheses. For example, 12-pentyl-1, 12-dicarba-closo-dodecaborane-1-carboxylic acid was synthesized from p-carborane via 1 in 62% overall yield, a considerable improvement over the 44% yield obtained by direct methods.
Databáze:	OpenAIRE
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