Rhodium-catalysed heterocycle synthesis

Rhodium-catalysed asymmetric cyclization/hydroboration followed either by Pd-catalysed arylation or by oxidation was applied to the synthesis of a number of chiral, non-racemic carbocycles and heterocycles. Thus, reaction of enyne (28) with catecholborane, catalysed by a 1 1 mixture of [Rh(COD)2]+ Sbly,- and (S)-BINAP (5 mol%), followed by Pd-catalysed arylation with /7-IC6H4CF3, afforded benzyli-denecyclopentane (29) in 65% yield with 88% ee.46... 

Rische T, Muller K, Eilbracht P (1999) One-pot synthesis of pharmacologically active diamines via rhodium-catalysed carbonylative hydroaminomethylation of heterocyclic allylic amines. Tetrahedron 55 9801-9816... 

Rapoport and co-workers have reported a general synthesis of nitrogen, oxygen, and sulphur heterocycles (218) by rhodium-catalysed intramolecular N-H, 0-H, or S-H insertion reactions.of keto-ester precursors (217)- This reaction is well documented as an efficient route to B-lactams but this group has now shown that the reaction works well for the synthesis of five-and six-membered nitrogen heterocycles (Scheme 22). The reaction fails for seven-membered nitrogen heterocycles in this case C-H insertion to give a eyelopentanone is the preferred reaction mode. 

A synthesis of 4//-quinolizines from 2-vinylpyridine and alkynes catalysed by rhodium-Af-heterocyclic carbenes has been reported (Scheme 157). ... 

A 2-aminodiaryl ether (79.2, X = O) is cyclized to the furopyridine (79.3, X = O) by using the Pschorr reaction—thermolysis ofa mixture of the diazonium salt and copper powder. The use of heterocyclic diazonium salts in organic synthesis has been reviewed [2980]. Rhodium(II) acetate catalyses the room-temperature cyclization of a-diazo-jS-oxo esters (79.4) by carbenoid insertion into a benzenoid C—H bond. 

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