Propargyl aldehyde diethyl acetal

The alkynylation of estrone methyl ether with the lithium, sodium and potassium derivatives of propargyl alcohol, 3-butyn-l-ol, and propargyl aldehyde diethyl acetal in pyridine and dioxane has been studied by Miller. Every combination of alkali metal and alkyne tried, but one, gives the 17a-alkylated products (65a), (65c) and (65d). The exception is alkynylation with the potassium derivative of propargyl aldehyde diethyl acetal in pyridine at room temperature, which produces a mixture of epimeric 17-(3, 3 -diethoxy-T-propynyl) derivatives. The rate of alkynylation of estrone methyl ether depends on the structure of the alkyne and proceeds in the order propar-gylaldehyde diethyl acetal > 3-butyn-l-ol > propargyl alcohol. The reactivity of the alkali metal salts is in the order potassium > sodium > lithium. 

Alkynyl ketones can be prepared using the former useful methodology. Starting from propargyl aldehyde diethyl acetals and benzotriazole under toluene reflux, l-(benzotriazol-1-yl) propargyl ethyl ethers were prepared in 83-84% yield. The deprotonation is very... 

Dehydrohalogenation [1, 1035-1037, at end]. In a general procedure for the conversion of alkenes into alkynes by bromination and dehydrobromination, Ward and van Dorp recommend sodium amide and liquid ammonia for the dehydrobromination step.103 The preparation of propargyl aldehyde diethyl acetal is an example ,cb... 

Our first goal was to develop a scaleable route to the single enantiomer propargylic alcohol. The racemic alcohol was readily produced on a multi-kilogram scale by alkylation of the phenol with inexpensive bromoacetaldehyde diethyl acetal, hydrolysis to the aldehyde, and addition of the acetylenic Grignard reagent. With this material at hand we developed an efficient bioresolution process that esterified the alcohol in the presence of Chirazyme L9 (Scheme 30.7).26 At this point... 

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