Spiro from 1,3 dicarbonyl

Nair and co-workers reported the diastereoselective synthesis of spiro y-butyro-lactones from 1,2-dicarbonyls [125]. The authors studied the reaction with 1,2-cyclohexane dione 230 which produces the desired lactone 232 in good yields Eq. 22a. Isatins 233 are more reactive, but the products 235 are obtained as a 1 1 separable mixture of diastereomers Eq. 22b. The Nair research group extended this methodology to include homoenolate addition to tropanone 236 to form bicyclic 5-lactones 238 Eq. 22c [126]. 

Both experimental and theoretical studies have been reported of fluoro-denitration and fluoro-dechlorination reactions using anhydrous tetrabutylammonium fluoride in DMSO. The absences of ion pairing and strong solvation are critical in contributing to the reactivity of the fluorinating agent24 Quaternary ammonium salts derived from cinchona alkaloids have been shown to be effective catalysts in an improved asymmetric substitution reaction of /1-dicarbonyl compounds with activated fluoroarenes. The products may be functionalized to yield spiro-oxindoles.25... 

There is no reason why ),6-difunctionalised compounds should not be made by conventional methods, essentially ignoring the 1,6-relationship. The symmetrical spiro ketone (28) disconnects to l,6 dicarbonyl compound (29) which could no doubt be made by cleavage of (30). An alternative approach is to disconnect the ring from the chain to give (31) easily made from butyro-lactone (32) (Table 25.1). 

Dicyanomethylene)-l,3-indanedione 254 reacted with Ph3p=C=C=X (291), to yield the corresponding pyran derivatives 292, where X is either O or Different products were obtained by reactions of 254 with 1,3-dicarbonyls. Depending on residues and R, spiro compounds 293 (obtained from 254 and dimedone) and294 or propellanes 295 were isolated. ... 

Reproduced with permission from Wang G-W, Gao J. Selective formation of Spiro dihydrofurans and cyclopropanes through unexpected reaction of aldehydes with 1,3-dicarbonyl compounds. Org Lett 2009 11 2385-8. Copyright (2009), American Chemical Society. 

In related work, the same researchers described a four-component domino reaction that allows the one-pot synthesis of highly complex spiro systems, i.e. spiro[indoline/acenaphthylene-3,4-pyrazolo[3,4-6]pyridine derivatives 59 and 60 from phertylhydrazine, 3-aminocrotononitrile, isatin or acenaphthylene-1,2-dione and cyclic 1,3-dicarbonyl compoimds, including cyclohexane-l,3-diones and barbituric or thiobaibituric acid, in the presence of ( )-camphor-10-sulphonic acid (CSA) as catalyst (Scheme 1.30). 

To close our discussion of stereoselective multicomponent routes to arenoquino-lizines, we will mention the work by Dixon leading to the one-pot, three-component synthesis of a highly functionalized spiro compound 95 from p-nitrostyrene, p-dicarbonyl compound 94, and 3,4-dihydroisoquinoline. The initial Michael reaction between the first two components in the presence of the bifunctional... 

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