Electrophilic aromatic substitution in the calix[n]arene series is a well-established procedure leading exclusively to para-substituted derivatives. An unprecedented regioselectivity of the mercuration reaction leading to the meta-substituted calix[4]arenes is described. These compounds represent a new type of substitution pattern in classical calixarene chemistry and open the door for the straightforward synthesis of inherently chiral receptors based on calixarenes.

Deamination of 7-(Me3N)-nido-7,8,9-C3B8H10 (1a) leads either to the parent tricarbollide anion [nido-7,8,9-C3B8H11]- (2 - ) or to the neutral tricarbaborane nido-7,8,9-C3B8H12 (2a), together with a small amount of 8-Me-nido-7,8,9-C3B8H11 (2b). Di- and trisubstituted derivatives of 2a, 7-(Bu t MeN)-10-Me-nido-7,8,9-C3B8H10 (2c), and 7-(Bu t MeN)-10,11-Me2-nido-7,8,9- C3B8H9 (2d) were obtained as byproducts from the methylation of both 7-(Bu t NH2)-nido-7,8,9-C3B8H10 (1b) and 7-(Bu t MeNH)-nido-7,8,9- C3B8H10 (1c) with MeI in THF under reflux. Heating of 1a and 2 - at 350 °C resulted in the rearrangement of the carbons on the open-face to give high yields of the isomeric tricarbollides 10-(Me3N)-nido-7,8,10-C3B8H10 (3a) and [nido -7,8,10-C3B8H11]- (4 - ), respectively. The structure of 3a was determined by an X-ray diffraction analysis, and the geometries of the parent compounds 2 - , 2a, and 4 - were optimized at the ab initio MP2(fc)/6-31G* level. The structures of all compounds also were secured by the excellent agreement between the experimental data and the IGLO/NMR calculations of the 11B chemical shifts for the parent compounds at the DZ//6-31G*, DZ//MP2/6-31G*, and II‘//MP2/6-31G* levels.