Boranes stannyl

Hydrolysis of 1-boronylallylstannanes, available by stannylation of alkenyl and allyl boranes. gives (Z)-allylstannanes stereoselectively34. 

Dialkynylstannanes were synthesized and characterized by their NMR spectra. These compounds react with boranes yielding l-stanna-4-bora-2,5-cyclohexadienes (97), stan-noles (98), as shown in reaction 24, and stannolines (99), as shown in reaction 25. When R 4 H it is possible to isolate at low temperature the tautomeric intermediates 95 and 96 of reaction 23, one of which is a TT-stabilised stannyl cation complex279. Application of the same borane derivatization scheme to tetraalkynylstannanes leads to formation of 1-stannaspiranes where the rings are combinations of 97, 98, and 99 structures116,280. 

The stannyl derivatives of the higher boranes have been reviewed, this field. 

CJH17BN2O, Borane, (ethylcarbaraoyl)-compd. with trimethylamine (1 1), 25 83 CaHi8N2SSn2, Sulfur diimide, bis(trimethyl-stannyl)-, 25 44... 

Reduction using boranes. A practical modification of the oxazaborolidine-catalyzed reduction of ketones with borane is to replace the trialkylborane component with trimethyl borate. For the reduction of (3-silyl and ( -stannyl enones the use of 80 is advocated. ... 

Stannyl derivatives have also been prepared from higher boranes.50 For example, Li+B5H8 reacts with trimethyltin chloride to give p-Me3SnB5H8 (19-8), in which the bridging nature of the stannyl groups is inferred from the H and nB NMR spectra.51... 

The reaction is quantitative in terms of (TPE)2CoX2 produced and )delds the stannyl borane in 60% yield after work up ... 

Iron carbonyl fragments have been incorporated into many heterometallic borane and carborane compounds. Those compounds are covered in Chapter 3.05 and will not be discussed here. Simple boryl adducts have been reported from the reaction of Na2Fe(CO)4 and ClBCat" (Cat = catecholate or a Bu-substituted derivative. Equation (8)). The same products can be obtained upon irradiating Fe(CO)s and Cat B-BCat" in toluene at 0°C. Reaction of the diboryl 6 with 1 equiv. of lithium bis(trimethylsilyl)amide in toluene solvent leads to removal of one boryl unit and the formation of an anionic iron boryl complex (Equation (9)). The anionic species can also be obtained by stoichiometric addition of the ClBCat complex to Na2Fe(CO)4. Reaction of [Fe(CO)4 B(3,5-/-Bu2-Cat) ] with ClSnMes gives the stannylated derivative Fe(CO)4 B(3,5-/-Bu2-Cat) (SnMe3). 

Organoboration studies of a variety of substituted stannyl alkynyl derivatives have led to a new fused heterocycle, chiral alkenyl-(N-azolyl)boranes,boron substituted slla and germa cyclopentadienes, two isomeric highly substituted boroles ... 

The compound phenalenyl(dipropyl)borane has been studied by NMR spectroscopy. The interest in this work is that two different [1,3]-B shifts are observed, implying fluxionality in the compound. The behaviour of this species is at odds with the behaviour of the trialkyl-silyl and -stannyl analogues. The first... 

There have been significant discoveries of methods that enable the enantioselective addition of an alkyne to an aldehyde or a ketone [182]. The resulting chiral propargyl alcohols are amenable to a wide variety of subsequent structural modifications and function as useful, versatile chemical building blocks. In 1994, Corey reported the enantioselective addition reactions of boryl acetylides such as 292, prepared from the corresponding stannyl acetylenes (e.g., 291) in the presence of the oxazaborolidine 293 as the chiral catalyst (Scheme 2.36) [183]. Both aliphatic and aromatic aldehydes were demonstrated to participate in these addition reactions, which proceeded in high yields and with impressive enantioselectivity. The proposed transition state model 295 is believed to involve dual activation both of the nucleophile (acetylide) and of the electrophile (aldehyde). The model bears a resemblance to the constructs previously proposed for alkylzinc addition reactions (Noyori, 153) and borane reductions (Corey. 188). 

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