Boranes ethylene derivs., synthesis

Reaction of boranes with diazo compounds Synthesis of ketones from ethylene derivatives... 

Cyanogen bromide borane Synthesis of tran -ethylene derivs. from acetylene derivs. 

Tri(cyclopentyl)borane in diglyme added at 0° to Li-n-hexylacetylide under hexane, the volatile solvent removed, methyl tosylate added at -78°, the cooling bath removed, warmed 2 hrs. at 40°, then oxidized with alkaline H2O2 -> product. Y 88%. F. e., also with other alkylating agents such as bromides, sulfates, or oxonium salts, protonation with methanesulfonic acid, and synthesis of mixtures of cis- and trans-ethylene derivs., s. A. Pelter, C. R. Harrison, and D. Kirkpatrick, Chem. Commun. 1973, 544. 

The development 0/ the chemistry of boranes continues with outstanding results It has produced a convenient route to the less stable, terminally unsaturated compounds from the more stable, highly substituted ethylene derivatives , a facile procedure for the asymmetric synthesis of alcohols of high optical purity , and a... 

Via intermediates Synthesis of hydrocarbons from ethylene derivatives via boranes A new general coupling reaction... 

Coupling of ethylene derivatives via boranes Synthesis of 0x0 compounds from ot,/ -ethylenoxo compounds... 

Support-bound 1,2-diamines can be readily converted into imidazolidinones by treatment with carbonyl diimidazole [128,129]. The required diamines have been prepared on cross-linked polystyrene by reduction of peptides bound to MBHA resin with borane. Similarly, bicyclic imidazolines have been prepared from triamines and thiocarbonyl diimidazole (Entry 10, Table 14.3). Dehydration of polystyrene-bound monoacyl ethylene-1,2-diamines yields 4,5-dihydroimidazoles (cyclic amidines, Entry 5, Table 13.18). Several groups have reported the synthesis of 2-aminoimidazol-4-ones from resin-bound amino acid derivatives (e.g., Entry 6, Table 15.11). Most of these compounds are, however, unstable, and slowly decompose if dissolved in DMSO (Jesper Lau, private communication). 

Monaharan has developed a versatile synthetic route for the synthesis of 2 -0-[(N, iV-dimethylamino)-oxyethyl] modified purine and pyrimidine nucleoside phosphoramidites (63a-d) to be used as antisense oligonucleotide building blocks. In the syntheses of the purine-based analogues, the (iV, N-dimethylamino)-oxyethyl group was introduced via a 2 -allyloxy nucleoside intermediate, while the pyrimidine-based nucleosides were obtained from the TBDMS-protected 2,2 -anhydro-5-methyluridine via ring opening reaction in the presence of borane and ethylene glycol. The aminoxy derivatives were... 

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