D. Devaprabhakara

Dihydrobation-chromium trioxide oxidation of gem-and vic-diorganoboranes

Abstract Representative cyclic and acyclic acetylenes were hydroborated using BH 3 —THF, and the resulting mixture of 1,1- and 1,2-diorganoboranes was treated with chronium trioxide in pyridine. It appears that the 1,1-diorganoboranes are transformed to the corresponding alcohols and ketones, while the threo -1,2-diorganoboranes mainly give ( E )-olefines via a cis stereospecific elimination.

Reactions of disiamyl(3-phenyl-2-butenyl)borane with aldehydes and ketones

A substituted allyl organoborane, disiamyl(3-phenyl-2-butenyl)borane has been prepared in situ by the monohydroboration of 3-phenyl-1,2-butadiene with disiamylborane. It reacts readily with butyraldehyde, benzaldehyde, acrolein and acetone to give unsaturated alcohols, possibly via a six-membered transition state involving allylic rearrangement.

Oxidation of organoboranes with pyridinium chlorochromate: a facile synthesis of ketones from alkenes

Organoboranes from cyclic alkenes on oxidation with an excess of pyridinium chlorochromate provide ketones in high yield.

The cis,cis-1,5-cyclononadiene complexes of silver(I), copper(I) and rhodium(I) salts

The syntheses and spectral properties of cis,cis-1,5-cyclononadiene complexes of silver(I), copper(I) and rhodium(I) are described.

Regiospecific functionalization of cyclic allenes with catecholeorane

Abstract Reaction of diborane1 and disiamylborane2 with cyclic allenes, resulted in the formation of a mixture of products resulting from the addition of boron at the central carbon as well as terminal carbon. Fish has reported that addition of 4, 4, 6-trimethyl-1, 3, 2-dioxaborinane to 1, 3-disubstituted allenes takes place at the central carbon atom preferentially when the hydroboration was done at 130° for 35–50 h in a sealed tube.3 The reactivity and stability of catecholborane at high temperatures which is known to provide greater stearic

Syntheses of (E, E)-1,4-diaryl-1,3-butadienes

trans-β-Phenylethenylboronic acid, trans-β-p-methylphenylethenylboronic acid and trans-β-p-methoxyphenylethenylboronic acid on treatment with catalytic amounts of palladium chloride in presence of excess of lithium chloride and triethylamine give the corresponding (E, E)-1,4-diaryl-1,3-butadienes in virtually quantitative yield.

Chromic acid oxidation of bicyclic organoboranes

Bicyclic organoboranes(9-borabicyclo[3.3.1]nonane, 10-borabicyclo[4.3.1]decane and 11-borabicyclo[5.3.1]undecane) on oxidation with an excess of aqueous chromic acid give monocyclic ketones. A mechanism is proposed to account for the formation of this unexpected product.

π-complexes of cis,cis-1,4-cyclononadiene

The syntheses and spectral properties of the cis,cis-1,4-cyclononadiene π-complexes copper (I), Palladium(II) and platinum(II) are described. The diene does not give an isolable silver(I) complex. The attempted rhodium(I) complex formation of the diene gives the rhodium(I) complex of cis,cis-1,5-cyclononadiene.

Carbonboron bond cleavage in allyl orgnaoboranes

Abstract Allylic rearrangement has been shown to occur during protonolysis of ally organoboranes obtained from monohydroboration of monosubstituted and 1,1-disubstituted acyclic allenes with disiamylboranc 1

Dihydroboration of cyclic allenes

The study on the dihydroboration of a large ring cyclic allene, 1,2-cyclotridecadiene and the smallest stable allene, 1,2-cyclononadiene is described. For example, a mixture of products containing isomeric cyclotridecene, bicyclo(10.1.0)-tridecane, cyclotridecanone, cyclotridecanol, isomeric cyclic 1,2-cyclotridecandiol and isomeric 1,3-cyclotridecandiol is obtained from dihydroboration-oxidation of 1,2-cyclotridecadiene. However, dihydroboration-hydrolysis-oxidation of 1,2-cyclotridecadiene affords mainly cyclotridecanol, whereas dihydroboration-oxidation with chromium trioxide-pyridine yields mainly a mixture of Z- and E-cyclotridecene. Reasonable mechanistic pathways have been suggested for the formation of products. The proposed unusual elimination reaction of 1,2-diorganoboranes with chromium trioxide has been substantiated using an authentic 1,2-diorganoborane from diphenyl acetylene. The reaction appears to be stereospecific withthreo-diorganoborane furnishing predominantly E-alkene. The results with 1,2-cyclononadiene has also been rationalised on a similar basis.