ChemInform Abstract: Recent Advances in the Field of Camouflaged Carboranes and Polyhedral Boranes

Abstract

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Synthesis of closo-1,2-H2C2B8Me8 and 1,2-H2C2B8Me7X (X = I and OTf) Dicarbaboranes and Their Rearrangement Reactions

“…This work is the first venture into the area of B-methylation chemistry of compounds derived from closo -1,2-H 2 C 2 B 8 H 8 ( 2a ). It was demonstrated that all B-positions in 2a can be furnished with methyl substituents to give closo -1,2-H 2 C 2 B 8 Me 8 ( 2c ) or closo -1,2-H 2 C 2 B 8 Me 7 X ( 2g – 2j ) carboranes via electrophilic reaction with MeI, in contrast to the bigger, 12-vertex 1,2- and 1,7-R 2 C 2 B 10 H 10 analogs in which two boron sites remain unmethylated. It was also shown that a similar B-permethylation of the 1,2-Me 2 C 2 B 8 H 8 ( 2b ) analog fails, most probably because of steric and electronic effects of the two adjacent CMe groups rather than for kinetic reasons.…”

“…On the other hand, B-substitution processes on 2 pertinent to this work have so far been very scarce, being restricted to a few reactions with halogenation agents to afford 7-, 10-, and 7,10-substituted derivatives . Several successful B-methylation experiments in the monocarba- and dicarbaborane series, together with those achieved later by our group in the B-permethylation of the ten-vertex dicarbaboranes closo -1,6-C 2 B 8 H 10 , closo -1,10-C 2 B 8 H 10 , and arachno -6,9-C 2 B 8 H 14 , prompted us to extend boron-methylation strategy to the remaining closo -isomer 2 . Special attention will be paid to the permethylation of B-vertices and thermal rearrangement reactions under the formation of hydrocarbon–boron hybrid structures of egg shape that exhibit a surprisingly high stability .…”

Electrophilic Methylation of Decaborane(14): Selective Synthesis of Tetramethylated and Heptamethylated Decaboranes and Their Conjugated Bases

“…In the current area, only one alkylated structure of 1 is available, namely, 1-Et- nido -B 10 H 13 . In addition to that, the list of iodo, and/or other halogeno (X) and trifluoromethylsulfonyl (OSO 2 CF 3 ), derivatives of 1 is limited to a few examples, e.g., the substituted lowest rim of 1 (i.e., I bonded either to B1 or to B2) − and the substituted upper rim of 1 (i.e., H in B6 and/or B9 positions substituted with X or OSO 2 CF 3 , , and Br bonded to B5 and B10). , In view of the recent permethylation or persubstitution methods reported by our − or other − laboratories, we have now tried to extend these synthetic strategies to compound 1 , a key species of the borane series, also taking into account that the methylation of the boron clusters usually provides more stable species suitable for further examinations.…”

Quantitative syntheses of permethylated closo-1,10-R2C2B8Me8 (R = H, Me) carboranes. Egg-shaped hydrocarbons on the Frontier between inorganic and organic chemistry

“…2 ) and those leading to a series of halo derivatives 1,10-H 2 C 2 B 8 H 7 -2-X. 6 The successful B-methylation experiments in the 12-vertex carborane series, 7–9 together with those achieved by our group in the B-methylation of closo -1,6-C 2 B 8 H 10 , 10 arachno -6,9-C 2 B 8 H 14 , 11 prompted us to extend boron-methylation strategy to the most stable members of the 10-vertex closo series, closo -1,10-R 2 C 2 B 8 H 10 (1) (where R = H or Me), which have been now relatively easily available. 12 In this article we would like to present electrophilic reactions with methylation agents leading to quantitative permethylation of B-vertexes under the formation of rigid, hydrocarbon–boron structures of egg shape that exhibit outstandingly high stability.…”