Synthesis of symmetrical and unsymmetrical α, ω-bi-(3,3 -flavonyloxy)alkanes

Several symmetrical α,ω-bi-(3,3"-flavonyloxy)alkanes (3a-w) have been synthesised by treatment of variously substituted flavonols (1) with α,ω-dibromoalkanes [Br-(CH 2 ) n -Br, where n = 2 to 6] in the molar ratio 2:1. However, the reactants in the molar ratio 1: 1 furnished a mixture of (3) and a-(3-flavonyloxy)-ω-bromoalkanes (4). The latter (4) on treatment with flavonols of different substitution pattern (5) gave unsymmetrical α,ω-bi-(3,3"-flavonyloxy)alkanes (6a-y).