Addition of Zincated Hydrazone to Vinyl Grignard Reagent. Ketone Synthesis by One-Pot Assembly of Four Components

Carbometallation Reactions

“…On the other hand, the addition of delocalized organometallics such as allyl-or propargylzinc derivatives to vinylmagnesium halide, proceeds very smoothly at low temperature [10]. A similar pattern was found for the reaction between the zincated hydrazone 236-ZnBr and a vinyl-Grignard reagent, which easily takes place at 0 hC within 1 h, to give the bismetallated hydrazone intermediate 244 in near-quantitative yield (Scheme 7-149) [181].…”

Rh(I)-Catalyzed Cyclocarbonylation of Allenol Esters To Prepare Acetoxy 4-Alkylidenecyclopent-3-en-2-ones

“…Preparation of cyclohexane-based substrates began by alkylating the lithium enolate of dimethyl hydrazone 4 , with the corresponding halides or triflates 5a-c (Scheme 2). 12 Acidic hydrolysis with oxalic acid gave ketones 6a and 6c (n = 1, 3) in 44% and 83% yield. 13 Ketone 6b was obtained in only 5% yield, possibly due to a competing E2 elimination of the triflate to form an enyne.…”

Carbozincation Reactions of Carbon–Carbon Multiple Bonds

“…The reaction mixture was then treated with iodine. The crude product was purified by silica gel chromatography (pentane) to give the major diastereomer (209 in anhydrous THF (10-15 mL) was cooled to −40 ∘ while 1.6 M n-BuLi (hexanes, 1.1-1.3 equiv) was added dropwise. The color of the solution immediately turned yellow-orange.…”