Table 3.

Ring contraction substrate scope.

Entry	Substrate 10	R1	R2	Product 1	Overall Yield [%][e]
1[a,d]	10a	–CH3	–CH2CH=CH2	1a	84
2[a,d]	10b	–CH2CH3	–CH2CH=CH2	1b	90
3[a,d]	10c	–CH2Ph	–CH2CH=CH2	1c	86
4[a,d]	10d	–CH2C≡CH	–CH2CH=CH2	1d	95
5[a,d]	10e	–CH2CH2CH=CH2	–CH2CH=CH2	1e	87
6[a,d]	10f		–CH2CH=CH2	1f	91
7[a,d]	10g		–CH2CH=CH2	1g	92
8[a,d]	10h	–CH2CH2CN	–CH2CH=CH2	1h	85
9[b,d]	10i		–CH2CH=CH2	1i	80
10[a,d]	10j		–CH2CH=CH2	1j	87
11[c,d,f]	10l	–CH2OTBDPS	–CH2CH=CH2	1l	91
12[c,d,g]	10m	–(CH2)3OTBDPS	–CH2CH=CH2	1m	85
13[c,d,h]		10n	1n		81
14[a,d,g]		10o	1o		87

^[a]Reduction Conditions A: vinylogous ester (1.0 equiv), LiAlH₄ (0.55 equiv) in Et₂O (0.2 M) at 0 °C, then 10% aqueous HCl quench.

^[b]Reduction Conditions B: 1) vinylogous ester (1.0 equiv), DIBAL (1.2 equiv) in PHCH₃ (0.03 M) at −78 °C; 2) oxalic acid•2H₂O in MeOH (0.02 M).

^[c]Reduction Conditions C: vinylogous ester (1.0 equiv), CeCl₃•7H₂O (1.0 equiv), NaBH₄ (3.0 equiv) in MeOH (0.02 M) at 0 °C, then 10% aqueous HCl in Et₂O at 0 °C.

^[d]Ring Contraction Conditions: β-hydroxyketone (1.0 equiv), CF₃CH₂OH (1.5 equiv), LiOH (1.5 equiv) in THF (0.1 M) at 60 °C.

^[e]Isolated yield over 2–3 steps.

^[f]See Supporting Information for experimental procedures for substrate synthesis.

^[g]Prepared from 14k. See Supporting Information.

^[h]Prepared from 14a. See Supporting Information.