Table 1.

Screening of Catalysts and Diazo Reagents for the Cyclopropanation of Carvone (1).^a

entry	diazo	catalyst	% yieldb	drc
1	2a	Cu(acac)2	0	–
2	2a	IprCuCl	trace	–
3	2a	PdCl2(CH3CN)2	0	–
4	2a	Rh2(OCOCF3)4	20%	2:1
5	2a	Rh2 (OAc)4	28%	2:1
6	2a	Rh2 (esp)2	45%	2:1
7	2b	Rh2 (esp)2	19%	2:2:1:1
8	2c	Rh2(esp)2	55%	1:1:1:1
9d	2d	Rh2 (esp)2	91%	1:1:1:1

^aReaction of carvone (1) and diazo esters 2a–c, (4 equiv) at 22 °C.

^bValues refer to isolated yields.

^cRatios were determined by ¹H NMR (500 MHz); the relative stereochemistry was not determined.

^dOnly 1.2 equiv of 2d were used. acac = acetylacetonate; IPr = [1,3-bis(diisopropylphenyl)imidazole-2-ylidene]; esp = α,α,α′,α′-tetramethyl-1,3-benzenedipropionate.