Structural studies of organoboron compounds. XXXVII. 8,8-Pentamethylene-6-phenyl-6,9-epoxy-5,7-dioxa-8-azonia-6-borata-6,7,8,9-tetrahydro-5H-benzocycloheptene

Abstract

. Can. J. Chem. 68, 64 (1990).Condensation of equirnolar amounts of salicylaldehyde, N-hydroxypiperidine, and phenylboronic acid yields the title compound. Crystalsof 8,8-pentarnethylene-6-phenyl-6,9-epoxy-5,7-dioxa-8-azonia-6-borata-6,7,8,9-tetrahydro-5H-benzocycloheptenearemonoclinic, a = 12.773(1), b = 11.9600(7), c = 10.641 1(6)A, P = 103.786(7)", Z = 4, spacegroup P 2 , / c . The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.039 and R,, = 0.047 for 2420 reflections with I ? 3u(1). The compound has a bridged heterocyclic B,N-betaine structure with a PhB(OR)3 anionic centre. Bond lengths (corrected for libration) include: B-O(aryl C) = 1.481(2), B-O(alky1 C) = 1.488(2), B-O(N) = 1.539(2), and B-C = 1.591(2) A. Key words: organoboron, boron compounds, crystal structure. 64 (1990).La condensation de quantitks CquirnolCculaires de salicylaldChyde, de N-hydroxypiperidine et d'acide phtnylboronique fournit le compose mentionnC dans le titre. Les cristaux du 8,8-pentarn~thylkne-6-phCnyl-6,9-Cpoxy-5,7-dioxa-8-azonia-6-borata-6,7,8,9-tetrahydro-5H-benzocycloheptene sont rnonocliniques, groupe d'espace P 2 , / c , avec a = 12,773(1), b = 1 1,9600 (7) IntroductionThe reaction of equimolar amounts of salicylaldehyde, N-hydroxypiperidine, and phenylboronic acid leads to a 1 : 1 : 1 condensation product, the elemental analysis of which shows that 2 mole equivalents of water have been eliminated. This is consistent with the fact that the infrared and 'H nmr spectra show no evidence of free hydroxyl groups. On the basis of the elemental analysis and spectroscopic data several structures are possible for this compound. The absence of a C=O absorption in the infrared spectrum (solid state, KBr pellets) implies that the aldehyde function is involved in an intra-or intermolecular addition reaction resulting in the loss of the C=O double bond.The result could be a zwitterionic condensate 1 with a fivemembered cyclophenylboronate structure, or a six-membered phenylboronate ring system such as that in the N-oxide 2 or its --rearrangement 3 (which could also be formed directly by condensation of the three reactants).Both isomers, 1 and 2, could also be transformed by intra- The structure was solved by direct methods. The non-hydrogen atoms were positioned from an E-map and the hydrogen atoms from a subsequent difference Fourier synthesis. The non-hydrogen atoms were refined with anisotropic thermal parameters and the hydrogen atoms with isotropic thermal parameters. Scattering factors for all atoms were taken from ref.

A diphenylboron chelate of an ethylenebishydroxylamine formaldehyde adduct

“…The C1-O2 bond in the COBON ring [1.360 2Å] has considerable double-bond character (about 25%) (retained from the carbonyl moiety of the formaldehyde from which it derives); this results from back donation from oxygen to carbon The calculated bond order (Paolini, 1990) is 1.24, while that estimated from a bond-length versus bond-order plot (Häfelinger, 1970) is 1.27. This double-bond character in the C1-O2 bond of (3) is slightly greater than those of the corresponding C-O bonds in the COBON rings of the other compounds reported: 1.378 Å (Rettig et al, 1974) 1.387 Å (Kliegel et al, 1984), 1.380 Å (Kliegel et al, 1995), and 1.382 Å (Kliegel et al, 1990). In spite of the partially retained carbonyl π-bond, all these compounds exhibit shorter (stronger) B-O(C) bonds and longer (weaker) B-O(N) bonds, the differences ranging from 0.03 to 0.08 Å [for (3), B-O2(C1) = 1.487 (3) Å and B-O1(N) = 1.555 (2) Å].…”

“…The structure analysis establishes the molecular constitution (3) (R = 2-C 3 H 7 ), generated by an electrophilic attack of formaldehyde at the hydroxylamine N atom and subsequent (or simultaneous) chelate formation with diphenylborinic acid. Analogous COBON chelate ring systems have been found in the diphenylboron complexes of the reaction products from N,N-dimethylhydroxylamine and formaldehyde (Rettig et al, 1974) or acetone (Kliegel et al, 1984), acetone oxime and formaldehyde (Kliegel et al, 1995), and also, as part of a polycyclic ring system, from phenylboronic acid, N-hydroxypiperidine and salicyladehyde (Kliegel et al, 1990).…”

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

“…Examples of this type of adduct include the phenylboronate-stabilized cyclic adduct 7 (7), the diphenylborinate-stabilized amine-aldehyde adducts like 8 ( l l ) , and others (6, 12, 13). The crystal structure of an intramolecular tertiary amine-aldehyde adduct 9, stabilized by 3,5-dinitrobenzoic acid, has recently been published (14).…”

“…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). Moreover, a complex like 5 would represent a stabilized derivative of the labile zwitterionic '~revious paper in this series: ref.…”