Indoles 2-acylimidazoles

Simple bis(oxazoline) ligands, especially azabis(oxazolines), can catalyse the addition of indoles to benzylidene malonates in up to 99% ee, provided that excess of the chiral ligand is avoided.166 The paradigm followed in many asymmetric catalytic reactions that an excess of the chiral ligand with respect to the metal should improve enantioselectivity because the background reaction catalysed by a free metal is suppressed, was shown not to be applicable here,166 which might call for revisiting some of the many copper(II)-bis(oxazoline)-catalysed processes known. Enantioselective additions of pyrroles and indoles to ,/9-unsaturated 2-acylimidazoles catalysed by the bis(oxazolinyl)pyridine-scandium(III) triflate complex have been accomplished.167... 

In 2009, the general asymmetric coupling of substituted pyrroles (110) and indoles (208) with 2-acylimidazole substrate of type 200 was extended to other catalyst complexes such as 0.15-0.3 mol % of copper 4,4 -dimethyl-2,2 -bipyridine [Cu(dmbpy)]/DNA complexes [1.4—7 ug/niL DNA base pairs] in aqueous media. Good enantioselectivities (83-93%) of the corresponding adducts 202 and 209, respectively, were observed using sources of DNA such as st-DNA (salmon testes-DNA) and DNA-1 with the self-complimentary sequence of d(TCAGGGCCCTGA)2. A key limitation of this approach was the requirement of at least 5 1 ratio of arene to 200 to achieve good conversion to the adducts (no scheme provided) ... 

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