Phosponium salt

Tundo, P., and P. Venturello, Catalysis Mechanism of Phosponium Salts Supported on Silica Gel in Organic-Aqueous Two-Phase Systems, /. A/ner. Chem. Soc., 103, 856 (1981). 

Synthesis of diaryl heteroarotinoids (11) and (12) [27,30,31] began with a Lewis acid-catalyzed cyclization of tertiary alcohol (34) to give dihydroben-zothiophene (36) as the sole isolated product. The chemistry of the ensuing steps was similar to that used to prepare (9) and (10) and other diaryl heteroarotinoids and involved (a) Friedel-Crafts acylation of a fused aromatic-heterocyclic system, (b) reduction of the resulting ketone to a benzylic carbinol, (c) phosponium salt formation, and finally (d), Wittig coupling to methyl 4-formylbenzoate. The free acids (13) and (14) were obtained by saponification. 

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