Table 2.

Stereospecific copper‐catalyzed nucleophilic substitution of benzylic ammonium triflates with a silicon nucleophile.^[a]

Entry	Ammonium triflate	ee [%]	Benzylsilane	Yield [%][b]	ee [%][c]
1	(R)‐1 a	>99[d]		79	>99
			(S)‐4 aa
2	(R)‐1 b	98[e]		77	98
			(S)‐4 ba
3	(R)‐1 c	98[e]		76	98
			(S)‐4 ca
4	(S)‐1 f	98[d]		75	97
			(R)‐4 fa
5	(R)‐1 g	98[d]		71	98
			(S)‐4 ga
6	(S)‐1 h	98[d]		64	98
			(R)‐4 ha
7	(R)‐1 j	>95[e,f]		48	97[g]
			(S)‐4 ja
8	(R)‐1 l	99[d]		82	99
			(S)‐4 la
9	(R)‐1 m	99[d]		77	97
			(S)‐4 ma

[a] All reactions performed on a 0.25 mmol scale. [b] Yield of isolated product after purification by flash chromatography on silica gel. [c] Determined by HPLC analysis on chiral stationary phases after Tamao–Fleming oxidation. [d] Starting amine is commercially available in enantiomerically enriched form. [e] Determined by HPLC analysis on a chiral stationary phase at the stage of the free amine after amide formation with 4‐nitrobenzoic acid chloride (see the Supporting Information for details). [f] Racemization during amide formation; the enantiomeric excess is derived from the diastereomeric excess (de) of the highly diastereoenriched precursor10b (Ellman's tert‐butanesulfinyl amines9a). [g] The enantiomeric excess was determined at the stage of the silane; no Tamao–Fleming oxidation required.