The synthesis of carboracycles derived from B,B′-Bis(aryl) derivatives of icosahedral ortho-carborane

Reactions of both closo-9,12-I-2-1,2-C2B10H10 and closo-9,10-I-2-1,7-C2B10H10 with an excess of aryl magnesium bromide in the presence of [PdCl2(PPh3)(2)] afford the corresponding closo-9,12-(4-R-C6H4)(2)-1,2-C2B10H10 [R = H (1), Me (2), OMe (3), SMe (4), N(CH3)(2) (5), Cl (6)] and closo-9,10-(4R'-C6H4)(2)-1,7-C2B10H10 [R'=Me (7), OMe (8), N(CH3)(2) (9), Cl (10), and -C[(OCH2)(2)]CH3 (11)] compounds in high yields. ne anisole derivatives 3 and 8 were deprotected to yield the corresponding bis-phenols 12 and 13, respectively. Structural analyses of compounds 1, 3, 6, and 12 are reported. Re-etherification of compound 12 by using gamma-bromotriethyleneglycol methyl ether provided 14 (R = (CH2CH2O)(3)CH3). Oxidation of 4 with ceric(iv) ammonium nitrate (CAN) generated the bis-sulfoxide 15 (R=S(O)Me). Deprotection of compound 11 led to the corresponding acetyl derivative 18 (R'= C(O)Me). Bis-anisole 3 was tethered with 1,3-dibromopropane, 1,6-dibromohexane, 1,8-dibromooctane, 4,4'-bis(iodomethyl)-1,1'-biphenyl, and alpha,alpha'-dibromo-2,6-lutidine to afford the dimers 20b, 21b, 22b, 23b, and 24b, respectively. The tetrameric carboracycles 27 a and 30 a, as well as the dimeric 29c were obtained through repetitive coupling of the dimeric compounds 20b, 24b, and 22b with 1,3-dibromopropane, alpha,alpha'-dibromo-2,6-lutidine, and 1,8-dibromooctane, respectively. The tetrameric carboracycle 28a was obtained upon consecutive reactions of 1 with 1,4-dibromobutane. Hexameric carboracycle 28b was identified as a byproduct. Exhaustive ether cleavage of 27a generated octaphenol 31a. Re-etherification of 31a with trimethylenesultone provided the octasuffonate 32a, the first example of a water-soluble carboracycle. Linkage of dimer 23b with alpha,alpha'-dibromolutidine yielded the cyclic tetrameric tetrapyridyl derivative 30 a in low yield. The structures of the carboracycles 27 a, 28 a, 28b, and 30 a have been confirmed by X-ray crystallography. In addition, the compounds 28a,b are the first reported carboracycles that interact with solvent molecules in a host-guest fashion.