Indane synthesis

Ferraz HMC, Carneiro VMT, Silva LF Jr. Ring contraction of 1, 2-drhydronaphthalenes promoted by thallium(III) in acetonitrile a diastereoselective approach to indanes. Synthesis 2009 385-388. 

Hallberg and coworkers [84] developed a synthesis of monoprotected 3-hydroxy-indan-l-ones 6/1-156 in moderate to good yields using salicylaldehyde triflates and... 

Scheme 7. Synthesis of heterocyclic stibinogallanes and -indanes by dehalosilylation reaction.

On the other hand, in the synthesis of cholesterol (30) by Woodward and CO workers [10] the less stable fran -configuration between rings C and D is attained through a homosteroid (29). i.e. a steroid analogue in which the C/D indane system is substituted by a decalin in which the rran -configuration is the thermodynamically favoured (Scheme 8.7). The conversion of the six-membered ring into one of five members is carried out at a later stage, under conditions that do not affect the preformed tran -junction. 

Wells et al. reported almost twenty years ago on the reactions of chloro-gallanes and trimethylsilyl-substituted arsanes R 2AsSiMe3, which occurred under elimination of MesSiCl and subsequent formation of arsinogallanes of the types [Cl2GaAsR 2]%> RGa(AsR2)2 and Ga(AsR2)3 [23]. In 1988, Cowley et al. extended this reaction type to the synthesis of heterocyclic stibinogal-lanes and -indanes [21]. 

Molten sodium tetrachloroaluminate (a 1 1 mixture of NaCl and AICI3) is a good reaction medium for the Friedel-Crafts acylation reaction given in fig. 3.3 (Wade et al., 1979). Whereas the classical procedure for the synthesis of 1-indane from 3-phenylpropanoic acid consists of three reaction steps with a total reaction time of ca. six hours (Gattermann et al., 1982), the molten salt reaction is finished in five minutes and gives an even better yield (Wade et al., 1979). 

A one-step synthesis of isochromene itself has been reported from indene oxide (191) (66CC415). Irradiation of the epoxide in benzene affords two products, isochromene and indan-2-one, in similar quantities. It was proposed that initial fission of the carbon-carbon bond of the three-membered ring is followed by 1,4- or 1,2-hydrogen migration (Scheme 36). 

An alternative approach to the synthesis of isocoumarins which probably proceeds through the intermediacy of 2-carboxybenzyl ketones is based on the oxidative cleavage of indan-1-ones (76JCS(P1)1438). Although ozonolysis of the silyl enol ether (505) leads to the 2-hydroxy-2-methylindan-l-one (506), periodate oxidation of which gives the isocoumarin, a more convenient and direct route involves ozonolysis of the enol trifluoroacetate (Scheme 182). This synthesis is especially attractive for the preparation of isotopically labelled isocoumarins, since the precursors of the indanones, arylpropanoic acids or acrylophenones, are readily available bearing labels at specific sites. 

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