The preparation of [closo-1-CB9H8-1-COOH-10-(4-C3H7C5H9S)] as intermediate to polar liquid crystals

Abstract The preparation of iodo acid [ closo -1-CB 9 H 8 -1-COOH-10-I] − ( 1 ) is optimized and scaled from 1 to 40 g of B 10 H 14 . The improved preparation of the [ arachno -6-CB 9 H 13 -6-COOH] − ( 5 ) uses four times smaller volume and can be run conveniently in up to 40 g scale in a 3-L vessel. The optimized oxidation of 5 to [ closo -2-CB 9 H 9 -2-COOH] − ( 4 ) requires less oxidant, 12 times smaller volume, and significantly shorter reaction time. The overall yields of the iodo acid 1 as the [NMe 4 ] + salt are typically 8–10% (10–12 g) for 40 g of B 10 H 14 . The iodo acid 1 was transformed to amino acid 8 , then to dinitrogen acid 10 , and finally to sulfonium acid 2 [ 3 ] in overall yield of about 13%. The search for a more efficient phosphine ligand for the Pd-catalyzed amination process was not fruitful. Three routes to the sulfonium acid 2 [ n ] were investigated, and the best yield of about 47% was obtained for Cs 2 CO 3 -assisted cycloalkylation. Liquid crystalline ester of acid 2 [ 3 ] and 4-butoxyphenol was prepared and investigated.