A tricyclic analogue of indacrinone

The title compound is a uricosuric which is currently in clinical development by Merck. 

This synthesis, which was reported by a group of development chemists, represents a remarkably efficient application of asymmetric alkylation by chiral phase transfer catalysis (PTC) (see section 6.1.1). Reaction of indanone (77) and allylic halide (78) under PTC conditions in the presence of only a few per cent of chiral cinchonidine derivative 

The high enantioselectivity is ascribed to preferential ion-pairing on one enantiotopic face of the enolate of (77) with the chiral quaternary ammonium ion of the catalyst. The remaining steps consist of acid hydrolysis of the vinyl chloride and cyclisation to (81) (the Wichterle reaction) and installation of the acetic acid side-chain. It is likely that this asymmetric synthesis is actually used for large-scale production of the product. 

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