Methyl-2-propynyl carbonate

Methyl-2-propynyl carbonate (176) reacted with 2 mol of malonate 177 to give 2,3-disubstituted propenes 181 and 182 under neutral conditions in boiling THF (Scheme 11-48). The carbanion 177 attacks the central sp-carbon of the allenylpalladium to generate 178, which picks up a proton from malonate to form the jr-allylpalladium intermediate 180. The intermediate 178 can be considered as a palladium carbene complex (179). The malonate anion attacks the 7r-allylpaUadium 180 as expected, to give 181. Migration of the double bond in 181 affords 182 [43,44]. Thus the propargylic carbonate 176 has two... 

A Pd-catalyzed annulation of methyl 4-methoxyacetoacetate with methyl 2-propynyl carbonate yields a dihydrofuran, which can be converted directly to a furan (Scheme 21) <9381109>. 

Butyn-3-ol also reacts with carbon dioxide to give 1-methyl-2-oxo-propyl -1 -methyl -2 -propynyl carbonate and the cyclic carbonate 2.3-dioxycarbonyl-1-butene (Equation 19). 

The reaction of some nucleophiles occurs at the central sp carbon of the allenylpalladium. Soft carbon nucleophiles such as /3-keto esters and malonates react with propargylic carbonates under neutral conditions using dppe as a ligand (Scheme 24). 2,3-Disubstituted propenes are obtained by the reaction of methyl 2-propynyl carbonate with 2 moles of dimethyl malonate in boiling THE. Attack of the carbanion at the central sp carbon of the allenylpalladium generates the anionic <7--allylpalladium, which picks up a proton from the... 

Methyl 2-propynyl carbonate was prepared using a literature method. ... 

Propaigite [2312-35-8], 2-(/>-/W2-butylphenoxy)cyclohexyl 2-propynyl sulfite (145),is adark oil (d 1.1), is insoluble in water, and hydrolyzes in alkaline solutions. The rat oral LD5Q is 2200 mg/kg. Propargite is a widely used acaricide on fruits, vegetables, and row crops. Oxythioquinox [2439-01-2], 6-methyl-2,3-quinoxalinedithiol cycHc carbonate (146) (mp 172°C, vp 26 fPa at 20°C), is insoluble in water and soluble in organic solvents with rat oral LD5Qs of 1800, 1100 mg/kg. It is used as an acaricide for tree fruits. 

In order to study the mechanism of the furan formation, the following reactions were carried out. The reaction of isomeric 2-butynyl methyl carbonate (160) and 1-m ethyl propynyl methyl carbonate (161) with methyl acetoacetate (162) gives the same product 163. This shows that the furan formation from 160 and 161 proceeds via a common intermediate. 

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