Structural studies of organoboron compounds. XXIX. 6,6-Diethyl-2,2-diphenyl-1,3-dioxa-6-azonia-2-boratacyclooctane monohydrate

Abstract

. Can. J. Chem. 66, 109 1 (1988). Details of the preparation and structure of the title compound are given. Crystals of 6,6-diethyl-2,2-diphen 1-1,3-dioxa-6-azonia-2-boratacyclooctane monohydrate are orthorhombic, a = 7.0322(2), b = 16.3505(7), c = 16.8164(4) 1, Z = 4, space group P212121. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.045 and R,, = 0.050 for 2013 reflections with I 2 3 4 4 . The monocyclic eight-membered B, N-betaine is the first to be structurally characterized. The eight-membered chelate ring has a conformation intermediate between the S4 and boat-boat forms which is probably stabilized by transannular C-H...O interactions. The average libration-corrected 0-B and B-C bond lengths of 1.500 and 1.639 A are, respectively, the shortest and longest yet observed for an 0,O-chelate of diphenylboron.WOLFGANG KLIEGEL, STEVEN J. RETTIG et JAMES TROTTER. Can. J. Chem. 66, 1091Chem. 66, (1988. On rapporte les dCtails de la priparation et de la ditermination de la structure du compost mentionne dans le titre. Les cristaux du monohydrate du diCthyl-6,6 diphknyl-2,2 dioxa-1,3 azonia-6 borata-2 cyclooctane sont orthorhombiques avec a = 7,0322(2), b = 16,3505(7) et c = 16,8164(4) A, Z = 4 et groupe d'espace P212121. On a rCsolu la structure par des mkthodes directes et on l'a affinCe par la mCthode des moindres carrCs (matrice entibre) jusqu'a des valeurs de R = 0,045 et R, = 0,050 pour 2013 rkflexions avec I 2 3 4 4 . La B,N-bCtai'ne monocyclique h huit chainons est la premikre a avoir Ct C caracttriste du point de vue de sa structure. Le chtlate cyclique a huit chaions possbde une conformation qui est intermtdiaire entre les formes S4 [Traduit par la revue] Introduction 1,3-Dioxa-6-aza-2-boracyclooctanes 1 are known to undergo intramolecular (transannular) N+B coordination to give very stable bicyclo[3.3 .O]octane ring systems 2, confirmed by chemical and physical investigations (1-6). Generally the extent of the N+B interaction depends on the nitrogen and boron substitution as well as on the conformational conditions. The size and the electronic effects of the substituents markedly influence the magnitude of N-B coordination. In accordance with these findings, replacement of the ring nitrogen atom by oxygen or sulphur led to fairly unstable non-crystalline compounds without any detectable transannular bonding (7).A cyclooctane system without a transannular N 4 B interaction should be realized by quaternization of both the tertiary amine and boronate groups of 1. Direct N-alkylation and B-arylation of the known (8) compound 112 seemed disadvantageous, so the synthesis of 3 was carried out by N-alkylation of 2-diethylaminoethanol 6 via the addition of oxirane (ethylene oxide) and subsequent trapping of the zwitterionic intermediate 4 as the diphenylboron chelate 3. The symmetrical cyclic B,N-betaine structure 3 has been postulated in a preliminary report (9) on the basis of 'H nrnr data which suggest magnetically equivalent ethylene moieties with...

Structural studies of organoboron compounds. XXX. 1,9-Dimethyl-3,5,7-triphenyl-2,4,6,8-tetraoxa-1,9-diazonia-5-bora-3,7- diboratatricyclo[5.4.0.03,9]undecane

“…An X-ray crystallographic 'Part XXIX: ref. 47. 2~ompound 3 has been synthesized by reduction of the bis(Nmethy1)nitrone of glyoxal(3) with potassium tetrahydroborate.…”

Structural studies of organoboron compounds. XXXIV. 4-(N-Methoxymethylimino)-2,2-diphenyl-1,3-dioxa-2-borata-1,2,3,4-tetrahydronaphthalene and 4-diethylimino-2,2-diphenyl-1,3-dioxa-2-borata-1,2,3,4-tetrahydronaphthalene

“…The B<(phenyl) distances are similar to those reported for other diphenylboron Q --B 4 chelates. The small differences between the B< distances in 4 and 9 (0.009 and 0.012 A, respectively) are typical for Ph2B chelates having (pseudo)axial and (pseudo)equatorial B-phenyl substituents (30)(31)(32)(33)(34)(35)(36) and were also observed in the structure of 1 (X = Ph) (I). As observed in every case, the pseudo-axial B< bond is longer than the pseudo-equatorial B< bond.…”

Structural studies of organoboron compounds LVIII. 4-(1′-azoniabicyclo[2.2.2]-octanyl)-2,2-diphenyl-2-borata-1,3-dioxa-1,2,3,4-tetrahydronaphthalene

“…A similar structure, 6, has been postulated for an intermediate borate complex in a reversible reaction during the boronic acid-catalyzed hydrolysis of an N-salicylidene amino acid (3). The importance of zwitterionic intermediates in the understanding of catalytic reactions in general (4) and enzyme-catalyzed reactions (3,4) in particular, as well as our interest in the structure and function of stable B,N-betaines (5,6), has motivated us to establish unambiguously the structure 5. The nucleophilic addition of the amine at the carbonyl group to form the 0,N-acetal moiety in 5 resembles the addition of a hydroxylamine at the salicylaldehyde carbonyl group leading to the product 7, the structure of which has been established by an X-ray crystallographic analysis (7).…”

“…C (11) 1.509 (6) of diethyl ether, crystallization starts spontaneously. One hour later the crystalline precipitate is filtered off and washed with diethyl ether.…”