A-alkylacroleins

A novel route to 2-fhioromethyl- and 2-hydroxymethyl-4-alkylfurans was reported. Treating a-alkylacroleins with 1-bromo-l-trimethylsilylethylene in the presence of butyllithium yields 33. Oxidation of both double bonds followed by reaction with MsCl provides the key intermediate 34 vkdiich on treatment with TBAF produces the desired conqioimds <96TL7437>. 

Fluoromethyl- and 2-hydroxymethyl-4-alkylfurans are accessible from a-alkylacroleins and 1-bromo-l-trimethyl-silylethylene in a four-step sequence (Scheme 15) <1996TL7437>. Lithiation and carbonyl addition leads to diallylalcohols 11. Epoxidation and mesylation provides the bis-epoxides 12, which can be transformed into fluoro-methylfurans (X=F) upon treatment with tetrabutylammonium fluoride (TBAF). In the presence of water, hydroxymethylfurans are formed (X = OH). 

Another way of controlling the acid strength of the Br0nsted acid sites is by changing the nature of the T atoms. For instance, a low acidity Boron ZSM-5 zeolite containing Ce is active and selective for isomerization of 2-alkylacroleins into 2-methyl-2-alkenals without skeleton isomerization (Eq. 1) [10],... 

Rhodium-catalysed hydroformylation of a 2-alkyl allyl alcohol or 2-alkylacrolein diethyl acetal forms a key step in a general synthesis of 3- and 4-aIkyl-2,3-dihydrofurans. ... 

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