New syntheses of dalbergichromene and dalbergin from vanillin via neoflavene intermediate
In this Letter, naturally occurring dalbergichromene and dalbergin were synthesized from a common neoflavene intermediate, which was derived from vanillin. The giving neoflavene intermediate was debenzylated with AlCl3 to yield dalbergichromene in 39% total yield, and it was oxidized by DDQ, and subsequently debenzylated by Pd(OH)2/C and cyclohexene in refluxing ethanol to give dalbergin in 31% total yield.