Dimethyl borine

In a similar reaction, vinyllithium reagents add to dimethyl borinates (dimethoxyboranes) to give adducts which decompose to alkenes on treatment with iodine. 

The reaction is not restricted to phosphorus, silicon, and boron compounds the tetrameric (NSEt) is, for instance, formed from ethylamine hydrochloride and sulfur dichloride (49). Nor is it restricted to nitrogen compounds the very stable cyclic phosphinoborines are formed by elimination of hydrogen from the dimethyl-phosphine borine complex (17). 

A number of oxygen and sulphur compounds are sufficiently powerful electron-pair donors to form borine adducts by reaction with diborane. Of these the unstable solid dimethyl ether borine, Me20+.BH3, used in the purification of diborane, is well known. 

Regiospecific synthesis of Mannich bases. Hooz and Bridson2 have described a new regiospecific3 synthesis of certain Mannich bases which involves first reaction of a trialkylborane with an a-diazoketone in THF to form an enol borinate (l)4 after evolution of nitrogen ceases, dimethyl(methylene)ammonium iodide (2) in DMSO is added. The Mannich base (3) is obtained in 85-100% yield after hydrolytic workup. Cosolvent DMSO is crucial for high yields. 

Borane-dimethyl sulphide solution (73 mmol, 2.74 m in THF) was added dropwise, with stirring, to the neat alkynylsilane (200mmol), keeping the reaction temperature below 20°C by use of an ice bath. The mixture was stirred for 2 h at 0-5 °C. At this time, the solution of the trialkenyl borane was diluted with THF (200 ml), and then anhydrous trimethylamine A/-oxide (240 mmol, dried by azeotropic distillation with toluene) was added over 5 min at ambient temperature. The resultant slurry was heated (bath temperature 75 °C) for 4h, and then cooled to ambient temperature. The enol borinate thus formed was hydrolysed by the addition of water (100 ml), followed by stirring for 5 min. The layers were separated, and the aqueous phase was extracted with ether (2x 100ml). The combined organic extracts were washed with brine and dried. Concentration and distillation gave the acylsilane (75-91%). 

CgHi3B7C0CS, Caesium 3 t cyclopentadienyloctahydro 4 carba 3 Cobalt-a-closo-nonaborate, 40B, 583 CgHi4BN3, 1,8,10,9-Triazaboradecalin, 34B, 362 CgHisBN, Hexamethylenetetramine-borine, 34B, 162 CgHigB2N2S2Si, 4,5 Bis(dimethylamino) 2,2 dimethyl l,3 dithia 2-sila-4,5-diboracyclopentane, 46B, 624 CgHigBaCluNg, 3,5 Dichloro 1,2,4 trimethyl-1,2,4,3,5-triazadiboroli-dine dimer, 46B, 621... 

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