An acyliminium ion approach towards the synthesis of β-substituted 3,4-dihydroisoquinolone propionates

Abstract A variety of α-methoxy amides were prepared either by selective reduction of the exocyclic carbonyl of a 2-acyl-3,4-dihydroisoquinolone and subsequent trapping of the resultant α-hydroxy amide with acidic methanol or by reacting the sodium salt of 3,4-dihydroisoquinolone with a functionalized α-chloro ether. These intermediates were reacted with 1- tert -butoxy-1- tert -butyldimethylsiloxy ethene in the presence of BF 3 ·Et 2 O providing access to β-substituted isoquinolone propionates in good yield.