Synthesis of benzannulated spiroacetals using chiral gold-phosphine complexes and chiral anions

The development of an asymmetric gold-catalysed dihydroalkoxylation strategy for the synthesis of the 3′H-spiro[chroman-2,1′-isobenzofuran] spiroacetal ring system 5 is described. Spiroacetal was generated in up to 87:13 enantiomeric ratio using chiral gold-phosphine complexes and chiral silver phosphate Ag(S)-TRIP.