Intramolecular insertions of metal carbenoids from diazo compounds

6 Intramolecular insertions of metal carbenoids from diazo compounds 

Ruthenium porphyrins are effective catalysts for the cyclization of A-tosylhydrazones via intramolecular carbenoid C-H insertion to afford azetidin-2-ones 2003OL2535, 2003TL1445 . A non-porphyrin-based ruthenium catalyst, [RuCl2(/ -cymene)]2, has been developed recently for catalytic carbenoid transformation 20050L1081 . A [RuCl2(/ -cymene)]2-catalyzed stereoselective cyclization of a-diazoacetamides 418 by intramolecular C-H insertion produced azetidin-2-ones 419 in excellent yields and excellent ( 99%) air-stereoselectivity (Equation 168). 

There are many studies on manganese(m)-promoted radical cyclizations 1995TL9039, 1998T12029 . The influence of chiral auxiliaries on the stereocontrol of radical cyclizations has been investigated 1995SL915, 1996T489 . Treatment 

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