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The Rh(2)(OAc)(4)-stabilized carbenoid derived from dimethyl diazomalonate has been found to insert into the N-H bond of sterically hindered secondary aliphatic amines to afford hindered tertiary aliphatic amines in quite satisfactory yields. For example dimethyl 2-(dicyclohexylamino)propanedioate was formed in 85% yield from dicyclohexylamine, and the severely hindered dimethyl 2-(2,2,6,6-tetramethyl-1-piperidinyl)propanedioate was formed in 38% yield from 2,2,6,6-tetramethylpiperidine. The Rh(2)(OAc)(4) - dimethyl diazomalonate reaction was found to work also for arylalkylamines and diarylamines. In these cases, small amounts of products resulting from formal insertion of the carbenoid into an aromatic C-H bond were detected. Substitution at ortho positions caused the yield of C-H insertion products to increase. Other diazo compounds, viz. ethyl diazoacetoacetate, 2-diazocyclohexane-1,3-dione, and 2-diazo-5,5-dimethylcyclohexane-1,3-dione, performed satisfactorily in Rh(2)(OAc)(4)-catalyzed reactions with arylalkylamines and diarylamines, but led to complicated reaction mixtures with dialkylamines.

The synthesis of tris(2,6-dihydroxyphenyl)amine diborate, 4, is reported. This compound contains a linear B...N...B array for which a symmetrical three-center two-electron (3c-2e) bond is possible. The X-ray crystal structure of 4 shows that 3c-2e bonding is, in fact, absent. Rather, the B-N-B array of 4 is unsymmetrical, having a 2c-2e B-N dative bond with the remaining boron pyramidalized outward and bonded to the oxygen of THF, i.e., 4 x THF. In THF solution, 4 displays temperature-dependent 13C NMR spectra from which a DeltaG++ of 11.6 kcal/mol at 262 K may be calculated. The dynamic process observed in solution corresponds to a bond-switching equilibrium in which the B-N bond oscillates between the two borons ("bell clapper"). Ab initio calculations indicate that the most likely pathway for the bond switch does not involve a 3c-2e B...N...B bond, but rather occurs by nucleophilic attack of THF on the datively bonded boron to generate 4 x (THF)2, lacking any B-N interactions, followed by loss of one THF. The B-N-B system of 4 sans the perturbing effect of solvent was also investigated computationally. The form of 4 containing a 3c-2e bond is found to be a transition state in the solvent-free bond-switch reaction of 4, lying 2.66 kcal/mol above 4. The stability of three-center bonds to in-line distortion (viz., X...Y...X --> X-Y.........X) is discussed from the point of view of the second-order Jahn-Teller effect.

Resorcinol is a solid having a reported mp of 109-110 °C. 1 Therefore, it was surprising to obtain by recrystallizing a sample of impure resorcinol from a mixture of chloroform and acetone a solid of mp 182-203 °C.Since acetone and resorcinol are both venerable organic compounds, rich with history, it is reasonable to suspect that the reaction of resorcinol with acetone had been studied previously. Indeed, to the best of our knowledge, this reaction was reported for the first time in 1892 by Causse. 2 He obtained a solid, mp 212-213 °C, analyzing as C 15 H 16 O 4 and forming a diacetate and a dibenzoate, for which he proposed structure 1. This was questioned in 1910 by Schmidlin and Lang who reported following Causse's procedure and obtaining a product (mp 230-240 °C) whose elemental analysis was consistent with the formula C 12 H 14 O 2 , i.e. a compound formed by condensation of one resorcinol with two acetones with loss of two waters. 3 No structure was proposed, however.Sen and co-workers 4 reported in 1930 that the reaction of acetone with resorcinol gave either 2 (mp 153 °C) or 3 (mp 165 °C) depending on the mole ratio of the reactants, 737