Spiro-dioxides, synthesis

The overall procedure of the spiro y-lactone and 7-lactone synthesis can be considered as a molecular-assembling process in which three simple independent species (i.e., a conjugated diene, a ketone, and carbon dioxide) are used to build a complex organic molecule in a well-controlled fashion. 

Type D Syntheses [C — C—S + C—N). Further examples of the synthesis of thiazolidin-4-ones, by allowing 2-mercaptoacetic acid to react with C=N-containing compounds, have been reported with azines, only one of the C=N groups reacted with carbodi-imides, 2-iminothiazolidin-4-ones were obtained with cyclic ketones and amines, 2-spirothiazolidin-4-ones were prepared. The reaction between fluorenylidene-anilines (A) and 2-oxothiiran 1,1-dioxide afforded the spiro-thiazolidin-4-one 1,1-dioxides (78), which could also be obtained by oxidation of the products that were formed by starting from (A) and 2-mercaptoacetic acid. ... 

The second stage of the synthesis of all-czs-fenestrindane 9 begins by contraction of the cyclohexanone ring of 227 by two-fold bromination followed by Favorskii rearrangement [93] (Scheme 46). Subsequent decarboxylation of the acrylic acid furnishes the all-ds-tribenzo[5.5.5.5]fenestrene 233 in moderate overall yield. This compound as well as the precursors 225 and 227 have been converted into a number of related fenestranes including all-cfs-tribenzo-[5.5.5.5j- and all-czs-tribenzo[5.5.5.6]fenestrane [93]. Finally, benzoannelation of 233 using tetrachlorothiophene-S,S-dioxide and subsequent reductive aro-matization furnished fenestrindane 9. The overall yield of the eight-step synthesis of 9 from spiro-triketone 223 is ca. 15%. 

Carboxylation has also been seldom used especially for the constmction of various spiro-8-lactones. Rieke et al. have developed a direct synthesis of spiro-8-lactones from conjugated dienes and epoxides [114,115] (Scheme 67). Treatment of 1,2-bis (methylene)-cyclohexane-magnesium reagent derived from diene 306, with an excess of ethylene oxide, gave intermediate 307, which upon reaction with carbon dioxide and hydrolysis afforded the spiro-8-lactone 308. 

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