Methyl boranes

Any residual doubt about the actual 7r-stabilization of such carbanions, that is, the question concerning the importance of resonance structure 52a, has been decisively banished by an XRD analysis of the lithium bis(12-crown-4) salt of dimesityl(methyl)borane (54).56 Noteworthy are the slightly elongated mesityl C—B bonds at 1.617 A (over those in Mes2BMe at 1.586 A) and the pronouncedly shorter methylene C—B bond at 1.444 A. Moreover, the C2BCH2 core atoms lie essentially in a plane. All these data support the view of 54 as a borataethene, just as structure 52a would imply. 

Methylammonium perchlorate, 0498 Methyl azide, 0458 Methyl 2-azidobenzoate, 2934 f Methylbenzene, see Toluene, 2787 4-Methylbenzyl chloride, 2954 Methylbis( 2-peroxo)rhenium oxide hydrate, 0494b Methylborondichloride, see Dichloro(methyl)borane, 0425b Methylborylene, 0424... 

Y. Mo, J. H. Jiao, P.v.R. Schleyer, J. Org. Chem. 69, 3493 (2004). Hyperconjugation Effect in Substituted Methyl Boranes An Orbital Deletion Procedure Analysis. 

Palladium [i/3-Bis-(dimethylannino)-methyl-boran]-dichloro- XIII/3c, 85... 

The acylation of the pinacol derivative of dihydTOxy[lithio(trimethylsilyl)methyl]borane with methyl benzoate has been recoided, No details were given due to difficulties in the isolation of the products. 

Janiak et al. found that dibromo(methyl)borane MeBBr reacts with Hpzx at room temperature in the presence of NEt3 and Tl(OEt) to form [Tl(MeTpx)] in high yield.132 For the synthesis of R2B(pzx) species, sufficient pyrazolate ion is required to be present to convert [R3B(pzx)j quickly to [R2B(pzx)2], otherwise the R2B(pzx) species will dimerize to the stable pyrazabole R2B( x-pzx)2BR2. 

Figure 3.16 NBO comparison of hyperconjugative stabilization of negative hyperconjugation in methyl amine, neutral hyper conjugation in ethane, and positive hyperconjugation in methyl borane at the M06-2X/6-311 ++C(d,p) level of theory. For the details of NBO calculations, see Chapter 4.

For an earlier study, see Apeloig, Y., Schleyer, P. v. R., Pople, J. A. (1977). Molecular orbital theory of the electronic structure of molecules. 35. p -Substituent effects on the stabilities of ethyl and vinyl cations. Comparison with isoelectronic methyl boranes. The relative importance of hyperconjugative and inductive effects. Journal of the American Chemical Society, 99,5901-5909. 

C22H39BF3NO3, Cyclohexyl(hydroxy)(trifluoroacetamido(dicyclohexyl)-methyl)-borane methanol solvate, 44B, 585 C22H68B2oN202Ti, Bis(tetramethylammonium) 4,4 -commo-bis(decahydro-1, 6-dimethyl-1,6-dicarba-4-titana-closo-tridecaborate) bis(acetone), 41B, 850... 

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