Selected data for the reaction between MA and HCp catalyzed by the complexes 2 and 3^a.

Entry	Cat.	Cat. loading (mol%)	T (K)	t (h)	Conv.b (%)	exo/endo	erc,d (R/S)
1	(rac)-2	10	298	6	92	95/5	—
2	(rac)-2	5	298	15	86	98/2	—
3	(rac)-2	10	273	24	82	83/17	—
4	(rac)-2	10	263	140	61	88/12	—
5	(rac)-3	10	298	12	90	94/6	—
6	(rac)-3	5	298	24	87	96/4	—
7	(ARh,RN)-2	10	298	8	97	93/7	>99/1

^aReaction conditions: catalyst, 1.16 × 10⁻³ or 2.32 × 10⁻³ mmol (5 or 10 mol%); MA, 23.0 × 10⁻³ mmol; HCp, 81.0 × 10⁻³ mmol and 10 mg of 4 Å MS, in 0.5 mL of CD₂Cl₂.

^bBased on MA. Determined by ¹H NMR.

^cDetermined for the exo isomer by integration of the ¹H NMR signals in presence of the chiral shift reagent (+)-Eu(hfc)₃.

^dAbsolute configuration of the major exo adduct (R at C2) was established by comparison of the aldehyde proton splitting in presence of (+)-Eu(hfc)₃ with previous work indicating the relative splitting of the (R)-exo and (S)-exo adducts.¹⁸