Boranes chloro

Bicyclo[3.3 l]nonan-9-one, (2,4-dinitrophenyl)hydrazone (8,9) (—) Monochloroborane diethyletherate Borane, chloro-, compound with ethyl ether (8), Borane, chloro-, compound with 1,1 -oxybis[ethane] (1 1) (9) (36594-41-9). 

Pis(trimethylsilyl)amino)chloro((trimethylsilyl)amino)borane [10078-93-0]... 

We have reported that the reaction of 2,4,6-tri(chloro)borazine CI3B3N3H3 with three equivalents of tris(isopropylamino)borane B(NHPr )3 led to the formation of 2,4,6-tri[bis(isopropylamino)boryl(isopropyl)amino]borazine 11 [Fig. 5(a)] in quantitative yield.26,27 The subsequent polycondensation carried out in vacuo up to 150°C, led to the formation of the polymer 12 containing B3N3 rings linked either through direct B—N interring bonds (minor pathway) or three-atoms —N—B—N— bridges... 

Advances in the use of anionic stereogenic phosphorus have been interesting. Acylation of lithium o-anisylphenylphosphide with chloro-formates bearing chiral alkyl groups provided a diastereomeric mixture that could be induced to undergo an inversion at phosphorus (at relatively low temperature) to form the more favorable diastereoisomer in a crystalline lattice.186 Subsequent conversion to the quaternary phos-phonium species was followed by removal of the acyl group and isolation of the chiral tertiary phosphine as the borane derivative (Equation 3.10). 

Two additional examples of the Suzuki coupling using diethyl (3-pyridyl)borane include the coupling with 4-chloro-2,3 -bipyridine l -oxide (40) to give terpyridine 41 [7] and the coupling with 1,8-dibromonaphthalene to afford a mixture of two atropisomers 42 and 43 of l,8-di(3 -pyridyl)naphthalene [33, 34], Interestingly, the N atoms in 42 and 43 provide enough steric and spectral differentiation to make the detection of atropisomers possible at room temperature. 

Miscellaneous spectral studies include e.s.r. spectra of chloro-phosphines (2)6 and vibrational spectra of various phosphines.6-8 N.m.r. studies include those of borane complexes of aryldichlorophosphines,9 and studies of the conformation of dichloro-(isopropyl)phosphine (3)10 and dichloro(ethyl)phosphine (4).10 These phosphines have the preferred conformations shown. Conformation has also been the theme of electron-diffraction work on the anhydride (5), which appears to have a staggered conformation.11 The electronic implications of a relatively short P—O bond and wide POP angle have been discussed.11... 

In addition to the electrophilic alkylation, the phosphinyl-benzophospho-lide 25 reacted also with sulphur, BH3-thf, and trimethylsilyl azide under selective conversion of the Ph2P-moiety to give the corresponding thioxophos-phorane, borane-adduct, and iminophosphorane, respectively [33, 37], and quaternisation with chloro-acetonitrile followed by deprotonation gave access to a zwitterionic phosphonio-benzophosphohde with an exocyclic ylide-substituent [37]. 

Benzylic halides are reduced very easily using complex hydrides. In a-chloroethylbenzene lithium aluminium deuteride replaced the benzylic chlorine by deuterium with inversion of configuration (optical purity 79%) [537]. Borane replaced chlorine and bromine in chloro- and bromodiphenylme-thane, chlorine in chlorotriphenylmethane and bromine in benzyl bromide by hydrogen in 90-96% yields. Benzyl chloride, however, was not reduced [5iSj. Benzylic chlorine and bromine in a jy/n-triazine derivative were hydrogeno-lyzed by sodium iodide in acetic acid in 55% and 89% yields, respectively [5i9]. 

A more recent example, which involves an enantiomerically pure compound, reverts to the original lead by incorporating a hydroxyl group on the benzylic carbon. Preparation of this close relative of ibutilide (5-3) uses the same starting material. Acylation of w-dibutylamine with the acid chloride from the treatment of (6-1) with tert-butylcarbonyloxy chloride leads to the amide (6-2). Reduction of the carbonyl group in this compound with chloro-(+)-diisopropylcamphemyl borane (DIPCl) proceeds to afford the R alcohol (6-3) in high enantiomeric exess. 

The reduction of (alkylamino)haloboranes using hydride reagents can provide a convenient route to (alkylamino)boranes for example, LiA1H4 has been utilized to prepare bis(dimethylamino)borane [23884-11-9] from chlorobis(dimethylamino)borane [6562-41-0] (68). When this same strategy is applied to (bis(trimethylsilyl)amino)chloro((trimethylsilyl)amino)borane [10078-93-0], the expected compound is obtained along with the formation of two... 

More recently, several groups prepared related methylene-bridged PBs by reacting R2PCH2Li derivatives (R = Me, Ph, f-Bu) with chloro-boranes... 

The structure of 73 was substantiated spectroscopically (5 nB = 82.5 ppm) and confirmed crystallographically. A centrosymmetric chloro-bridged dimeric structure with tricoordinate copper centers was observed. The pendant character of the borane is apparent from the rather long the B- Cu (3.05 A) and B- Cl (4.06 A) distances associated with a trigonal planar geometry around boron. Compared to related mononuclear palladium and rhodium complexes (see Section IV.B), the presence of the chloro-bridge disfavors the formation of Cl-B interactions (coordination mode F) in 73. 

Because they serve as versatile starting materials for a variety of other boranes, the dihalo boranes, particularly the fluoro and chloro derivatives, are the most important members of this class of compounds. Their chemistry, along with other pentafluor-ophenyl boron halides, has been reviewed recently from a personal perspective by Chi vers,15 whose PhD thesis described early explorations into the chemistry of these compounds. Most of the known literature on these compounds deals with pentafluor-ophenyl compounds, but the chemistry is likely extendable to other compounds with different AiF groups. 

The oxazolidin-2-ones 53 (R = H=CCH=CH2 or COEt) are obtained in a one-pot reaction of amino alcohol carbamates 52 with sodium hydroxide, followed by allyl bromide or propi-onyl chloride (94TL9533). A modified procedure for the preparation of chiral oxazolidin-2-ones 56 from a-amino acids 54, which avoids the hazardous reduction of the acids with borane and the intermediacy of water-soluble amino alcohols, is treatment of the methyl ester of the amino acid with ethyl chloro-formate to give 55, followed by reduction with sodium borohydride and thermal ring-closure of the resulting carbamate f95SC561). The 2-prop-ynylcarbamates 57 (R = Ts, Ac, Bz, Ph or allyl) cyclize to the methyleneoxazolidinones 58 under the influence of silver cyanate or copper(I) chloride/triethylamine (94BCJ2838). 

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