Dilithiated 2-(Chloromethyl)-3-tosylpropene: A New γ-Chlorinated Allyl Sulfone Dianion in Organic Synthesis

Add time:07/18/2019    Source:sciencedirect.com

Dilithiation of 2-(chloromethyl)-3-tosylpropene (1) with n-butyllithium at −90°C in the presence of DMPU affords the allylic dianion 2 which reacts with deuterium oxide or very reactive alkylating agents to give α,α-disubstituted products 3 or 4, respectively. Monoalkylation at the α-position followed by cyclopropanation reaction takes place with n-alkyl bromides to provide tosylated methylenecyclopropanes 5. The reaction of dianion 2 with aldehydes or electrophilic olefins occurs at the α-position followed by the corresponding annulation process obtaining tosylated 2,5-dihydrofurans 6 or cyclopentenes 8, respectively. When ketones are used as electrophiles, dianion 2 reacts at the γ-position yielding 3-(tosylmethylene)tetrahydrofurans 7. Reductive desulfonylation of compounds 5-8 with sodium amalgam or samarium(II) iodide to afford the corresponding desulfonylated derivatives 22-26 has been also studied.

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