Table 3.

Substrate Scope of Heterodimerization of Monosubstituted Ketenes with Disubstituted Ketenes.^a

entry (+)/(−)-3	cat.	R1	R2	R3	% yield	% eeb	Z:E c
1 (+)-3ad	TMSQ	Me	Ph	Me	57	94	>97:3
2 (−)-3a	MeQd	Me	Ph	Me	64 (87)e	98	>97:3
3 (+)-3b	MeQ	Me	Ph	Et	57	73	90:10
4 (+)-3b	TMSQ	Me	Ph	Et	60	93	69:31
5 (−)-3b	MeQd	Me	Ph	Et	62	98	84:16
6 (−)-3c	TMSQ	Me	Ph	Ph	61	96
7 (+)-3c	MeQd	Me	Ph	Ph	60	96
8 (+)-3df–h	MeQ	Me	Me	Me	79	91
9 (−)-3df–h	MeQd	Me	Me	Me	90	95
10 (+)-3e	TMSQ	Et	Ph	Me	43	>99	>97:3
11 (−)-3e	MeQd	Et	Ph	Me	40	>99	>97:3
12 (+)-3f	MeQ	Et	Ph	Et	73	70	91:9
13 (+)-3f	TMSQ	Et	Ph	Et	33	80	74:26
14 (−)-3f	MeQd	Et	Ph	Et	65	95	87:13
15 (R)-3g	MeQ	n-Pr	Ph	Et	61i	72	93:7
16 (S)-3g	MeQd	n-Pr	Ph	Et	37i	95	83:17
17 (R)-3h	MeQ	n-Bu	Ph	Me	54	74	>97:3
18 (R)-3h	TMSQ	n-Bu	Ph	Me	55	88	97:3
19 (S)-3h	MeQd	n-Bu	Ph	Me	64	94	>97:3
20 (R)-3i	MeQ	n-Bu	Ph	Et	51i	76	93:7
21 (S)-3i	MeQd	n-Bu	Ph	Et	43	95	84:16
22 (+)-3jj	MeQ	OAc	Me	Me	52	76
23 (−)-3jj	MeQd	OAc	Me	Me	57	91
24 (+)-3kk	MeQd	Me	TMS	Me	50	nd	78:22

^aOnly one heterodimer regioisomer observed in all cases by GC-MS analysis of crudes and NMR analysis of 3.

^bee determined by chiral HPLC.

^cZ:E ratio determined by GC-MS or ¹H NMR analysis.

^dSign of specific rotation; (+)-enantiomer or (−)-enantiomer.

^eReaction conducted on 4 mmol scale.

^fIn these cases 2 equiv of LiClO₄ was used as an additive.

^gIsolated as Weinreb amide derivative 4 due to volatility of heterodimer.

^h20 mol% of catalyst used.

ⁱIsolated yield for 2 steps after conversion to acid 5 through Pd/C-catalyzed hydrogenolysis (characterized as acid. See SI and ref. 20 for details).

^jIsolated as Weinreb amide 4 due to susceptibility to decomposition on silica gel.

^k1 equiv of LiClO₄ was used as an additive.