Microwave-assisted metal-catalyzed reactions of halogenated carboranes
Pa lladium - catalyzed Rosenmund - von Braun conditions were applied to iodinated carboranes to prepare the first examples of cyano substituted derivatives of 1 - carba - closo - dodecaborate ( - 1). Optimized microwave - assisted conditions with Pd(PPh 3 ) 2 Cl 2 and copper (I) cyanide formed [12 - CB 11 H 11 CN] - , [7,12 - CB 11 H 10 (CN) 2 ] - , and [7,8,9,10,11,12 - CB 11 H 6 (CN) 6 ] - with great selectivity; products were purified and isolated as [Et 4 N] + salts in up to 8 1% yield. The compounds were characterized by NMR ( 11 B, 1 H, and 13 C), LC - MS , and IR. Single crystal X - ray diffraction revealed the structure of the [Et 4 N][CB 11 H 11 CN] cage. Nitriles are known to undergo many organic reactions , and a preliminary investigation of hydrolysis of the cyano substituent revealed that the [12 - CB 11 H 11 COOH] - cage can be formed. This work also reports improved microwave assisted synthesis of halogenated and alkynylated carboranes along with attempted
reactions of these compounds.
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