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[reaction: see text] Vanadium pentoxide very effectively promotes the bromination of organic substrates, including selective bromination of some aromatics, by tetrabutylammonium bromide in the presence of hydrogen peroxide; mild conditions, high selectivity, yield, and reaction rate, and redundancy of bromine and hydrobromic acid are some of the major advantages of the synthetic protocol.

Copper(II) acetylacetonate immobilized in ionic liquids efficiently catalyzes the aza-Michael reaction of amines with a,b-unsaturated carbonyl compounds to produce the corresponding b-amino carbonyl compounds with great alacrity in excellent yields. The reactions are far more facile than those reported earlier. The recovered ionic liquid phase containing the copper catalyst can be reused for several cycles with consistent activity.Keywords: amides; amines; b-amino ketones; aza-Michael reaction; copper(II) acetylacetonate; esters; ionic liquids; a,b-unsaturated carbonyl compoundsThe aza-Michael reaction is one of the important reactions in organic chemistry especially for the synthesis of C À N heterocycles [1,2] containing the b-amino carbonyl functionality. Such a functionality [3] not only constitutes a component of biologically active natural products but also serves as an essential intermediate in the synthesis of b-amino ketones, b-amino acids and b-lactam antibiotics, in addition to its use in the fine chemicals and pharmaceutical sectors.[4] Because of the intrinsic importance of b-amino carbonyl compounds, they have attracted sustained attention in organic synthesis, and the methods of construction of the functionality have undergone a metamorphosis from the classic Mannich-type reactions to the more widely used conjugated addition of nitrogen nucleophiles to a,b-unsaturated carbonyl compounds [5] which is commonly known as the aza-Michael reaction. The classical Mannich-type reactions are certainly very powerful but need quite severe reaction conditions and are rather sluggish thereby limiting their use in practice.[6] The conjugated addition reactions are, in the contrast, atom economic and quite easy to operate. However, these reactions require either basic conditions [7] or acidic catalysts [8] which seem to be detrimental to the desired synthesis. In order to overcome some of the disadvantages, a good number of alternative procedures have been reported over the past few years using Yb(OTf) 3 , [9] and heterogeneous solid acids, [16] but the need for an environmentally benign and facile protocol still exists. Room temperature ionic liquids are acknowledged as eco-benevolent alternatives to volatile organic solvents and have also other useful properties like very low vapor pressure, wide liquid range, high thermal stability and possess highly conductive solvation ability for a variety of organic substrates and catalysts including Lewis acids and enzymes. [17,18] Recently, ionic liquids [19] and quaternary ammonium salts in water [19b] have been reported to efficiently catalyze the aza-Michael reaction. Considering all these, it was thought that a combination of a suitable catalyst immobilized in an ionic liquid would enable facile conjugate additions, as desired. Incidentally, our attention was drawn to this problem at a juncture when we were engaged [20] in the aziridination of olefins catalyzed by Cu(acac) 2 immobilized in ionic liquids. To the best of our knowledge, aza-Michael reaction...