Table 1. Grignard Reaction Followed by Oxidation to Yield Mono-Substituted Divinyl Ketones.

entry	R	aldehyde 5	alcohol 6 (%)a	ketone 7 (%)b
1	Me	5a	6a (99)c (82)d	7a (71)c
2	n-Pr	5b	6b (99)c	7b (62)c
3	Ph	5c	6c (98)c (86)d	7c (74)d
4	4-ClC6H4	5d	6d (100)c	7d (56)d
5	4-OMeC6H4	5e	6e (98)c	7e (53)d

^aReaction conditions for 6a–e: CH₂=CHMgBr, tetrahydrofuran (THF), 0 °C → room temperature (rt), 1 h.

^bReaction conditions: MnO₂, 4 Ȧ MS, CH₂Cl₂, 50 °C, 3 h (for 7a,b); DDQ, 4 Ȧ MS, dioxane, rt, 18 h (for 7c–e).

^cCrude yield.

^dIsolated yield (by column chromatography).