. Author manuscript; available in PMC: 2012 Dec 30.

Published in final edited form as: Tetrahedron. 2011 Dec 30;67(52):10234–10248. doi: 10.1016/j.tet.2011.10.031

Table 4.

Ring contraction substrate scope.^a,b,c,d,e


entry	substrate 7	reduction conditions	R¹	R²	product 1^e	yield (%)^f
1	7a	A	–CH₃	–CH₂CH=CH₂	1a	84
2	7b	A	–CH₂CH₃	–CH₂CH=CH₂	1b	90
3	7c	A	–CH₂Ph	–CH₂CH=CH₂	1c	86
4	7d	A	–CH₂C≡CH	–CH₂CH=CH₂	1d	95
5	7e	A	–CH₂CH₂CH=CH₂	–CH₂CH=CH₂	1e	87
6	7f	A		–CH₂CH=CH₂	1f	91
7	7g	A		–CH₂CH=CH₂		92
8	7h	A	–CH₂CH₂CN	–CH₂CH=CH₂	1h	85
9	7i	B		–CH₂CH=CH₂	1i	80
10	7j	A		–CH₂CH=CH₂	1j	87
11	7m	C	–CH₂OTBDPSⁱ	–CH₂CH=CH₂	1m	91
12	7o ^g	C	–(CH₂)₃OTBDPSⁱ	–CH₂CH=CH₂	1o	85
13		A			1p	81
14		A			1q	87
15	7n	D	–OH	–CH₂CH=CH₂	1n	25
16	7l	A	–F	–CH₂CH=CH₂	1l	0

Reduction Conditions A: vinylogous ester 7 (1.0 equiv), LiAlH₄ (0.55 equiv) in Et₂O (0.2 M) at 0 °C, then 10% aqueous HCl quench.

Reduction Conditions B: 1) vinylogous ester 7 (1.0 equiv), DIBAL (1.2 equiv) in PhCH₃ (0.03 M) at –78 °C; 2) oxalic acid·2H₂O in MeOH (0.02 M).

Reduction Conditions C: vinylogous ester 7 (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.

Reduction Conditions D: vinylogous ester 7 (1.0 equiv), DIBAL (3.3 equiv) in PhCH₃ (0.03 M) at –78 °C; 2) 10% aqueous HCl in Et₂O at 0 °C.

Ring Contraction Conditions: β-hydroxyketone 10 (1.0 equiv), CF₃CH₂OH (1.5 equiv), LiOH (1.5 equiv) in THF (0.1 M) at 60 °C.

Isolated yield over 2-3 steps.

Prepared from 7k.

^h Prepared from 7a.

ⁱ

TBDPS = tert-butyldiphenylsilyl, Ts = 4-toluenesulfonyl, DIBAL = diisobutylaluminum hydride.