Table 1.

Diastereometric Ratios for R′-SO-N=CH-R/SulfurYlide 1 Aziridinations and Computed Relative Energies of Transition States (kcal/mol) for Re versus Si Addition Steps.^a

Imine	R′	S stereocenterb	Rc	yield	drd	ΔΔE‡e
2	t-butyl	S	BDA	92%	> 95:5	+1.8
3	t-butyl	S	cyclohexyl	81%	61:39	+0.9
4	4-methylphenyl	S	BDA	80%	67:33	+1.1
5	t-butyl	R	BDA	88%	79:21	-1.2
ent-2f	t-butyl	R	ADB	94%	> 95:5	-1.8
ent-5f	t-butyl	S	ADB	89%	79:21	+1.2

^aExperimental data from Ref. [5].

^bConfiguration of sulfinyl sulfur atom.

^cBDA denotes the protected diol as shown in Figure 1, as derived from D-mannitol; ADB denotes the mirror image of BDA, as derived from ascorbic acid.

^dDetermined by ¹H NMR (crude reaction mixture).

^eΔΔE^‡ estimated as E(TS_Re) − E(TS_Si), based on ZPE-corrected B3LYP/6-311+G**(THF) energies. Positive value indicates Si TS favored, negative value indicates Re TS favored.

^fEnantiomers of imines 2 and 5, respectively. ΔΔE^‡ values are given by symmetry.