Clarke, LA,Ring, A,Ford, A,Sinha, AS,Lawrence, SE,Maguire, AR

2014

December

Organic & Biomolecular Chemistry

Enantioselective copper catalysed C-H insertion reaction of 2-sulfonyl-2-diazoacetamides to form gamma-lactams

Validated

WOS: 23 ()

ALPHA-DIAZOACETAMIDES INTRAMOLECULAR ADDITION CARBENE INSERTION DIASTEREOSELECTIVITY TRANSFORMATIONS DIAZOSULFONES DIRHODIUM(II) STEREOCONTROL CYCLIZATION SELECTIVITY

12

7612

7628

The first examples of asymmetric copper-catalysed intramolecular C-H insertion reactions of 2-sulfonyl-2-diazoacetamides are described; trans gamma-lactams with up to 82% ee are achieved with the CuCl2-bisoxazoline-NaBARF catalyst system. The reactions generally display high efficiency and high trans selectivity, and also a strong regiochemical preference for insertion to lead to the formation of 5-membered rings over 4-membered rings. In cases where there are competing C-H insertion pathways available, to form sulfolanes or thiopyrans, only the insertion into the amide chain to form gamma-lactams is observed. With phenylsulfonyl derivatives, a minor competing C-H insertion pathway leading to beta-lactams is seen; interestingly, changing the identity of the copper ligand changes the product ratio of beta/gamma-lactams. The copper catalysed reactions compare favorably in terms of efficiency and enantioselectivity to the corresponding reactions catalysed by commercially available chiral rhodium catalysts.

10.1039/c4ob01430h