Grignard reagents 2-butadienyl

Triol 984 is converted to acetonide 985 and the free hydroxyl group is sequentially oxidized to an aldehyde (986) with pyridinium chlorochromate and then to an acid under Jones conditions. Acidic workup furnishes the hydroxy butyrolactone 987. Treatment of THP-protected butyrolactone 988 with methyl Grignard reagent affords diol 989. Removal of the THP group, tosylation of the primary alcohol, and cyclization under basic conditions provides epoxide 990. Opening the oxirane ring with 2-(l,3-butadienyl)magnesium chloride in the presence of... 

The butadienyl Grignard reagent (141) reacts with oxirans to yield normal ring-opened products (142) and the rearranged allenic products (143) (Scheme 7). Steric factors greatly influence the product distribution, from 100% of (142 R = H, R = Me)toproductratiosfor (142)to(143)of 91 9[R R = (CH2)4] and 60 40 (R = R = Me). The presence of AICI3 also caused a remarkable... 

Despite early successes in substitution of sulfolenes, initial attempts to develop methods for the deprotonation/substitution of 3-sulfolenes using stronger bases such as NaH, BuLi, LDA, and Grignard reagents were unsuccessful. This is caused by cycloreversion of the labile a-carbanion (69) to the more thermodynamically stable butadienyl sulfinate (70) (Scheme 6.18). 

In our method, the N,N-diethyl butadienyl carbamates (1) reacts both regio and stereospecifically to methyl vinyl ketone to give the cyclohexene (II) in 89% yield, which in turn adds the Grignard s reagent (III), again regio and ste-... 

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