2.2- Dialkoxycyclopropanecarboxylic esters

Silyl enolates of a,a-dialkoxy ketones react with furans to form [3 4- 4] cycloaddition products in the presence of SbCls (Eq. 6) [17], Cycloaddition also occurs when 2,2-dialkoxycyclopropanecarboxylic esters and carbonyl compounds are treated with SbCls [18]. 

Dialkoxycyclopropanecarboxylic esters reacted with aldehydes or ketones in the presence of 1 equivalent of a Lewis acid at — 78 °C to furnish y-butyrolactones in good to excellent yields and diastereoselectivities. With 3,3-dimethyl or 3-unsubstituted esters cw-lac-tones strongly dominated the product mixture (typically > 90% On the contrary,... 

Aldol reactions. Highly functionalized carbonyl compounds are produced using diketene" and 2,2-dialkoxycyclopropanecarboxylic esters in these condensations. An intramolecular reaction provides access to 2-alkoxycarbonyl-2-cycloalke-... 

Addition to Various Electrophiles. Various Lewis acids promote the addition of the reagent to an allylic acetate, following a carbon-Ferrier rearrangement pathway. Tita-nium(IV) chloride promotes the addition of the reagent to 2,2-dialkoxycyclopropanecarboxylic esters to give 3-alkoxy-2-cyclopentenones (eq 13). ... 

Nucleophilic cleavage of the polarized cyclopropyl bond in various alkyl-substituted ethyl 2,2-dialkoxycyclopropanecarboxylates 1 was achieved by heating in methanol or ethanol. As expected, the donor-acceptor-substituted cyclopropane behaved as a 1,3-dipole and added the nucleophile at the donor-substituted carbon resulting in ortho esters 2. 

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