Three novel amphiphilic alloxazinium salts were prepared: 3-dodecyl-5-ethyl-7,8,10-trimethylisoalloxazinium perchlorate (1c), 1-dodecyl-5-ethyl-3-methylalloxazinium perchlorate (2b), and 3-dodecyl-5-ethyl-1-methylalloxazinium perchlorate (2c). Their catalytic activity in thioanisole (3) oxidation with hydrogen peroxide was investigated in micelles of sodium dodecylsulfate (SDS), hexadecyltrimethylammonium nitrate (CTANO3) and Brij 35. Reaction rates were strongly dependent on the catalyst structure, on the type of micelles, and on pH value. Alloxazinium salts 2 were more effective catalysts than isoalloxazinium salts 1. Due to the contribution of micellar catalysis, the vcat/v0 ratio of the catalyzed and non-catalyzed reaction rates was almost 80 with salt 2b solubilized in CTANO3 micelles. Nevertheless, the highest acceleration was observed with non-amphiphilic 5-ethyl-1,3-dimethylalloxazinium perchlorate (2a) in CTANO3 micelles (vcat/v0 = 134). In this case, salt 2a presumably acts as a phase-transfer catalyst bringing hydrogen peroxide from the aqueous phase into the micelle interior. Synthetic applicability of the investigated catalytic systems was verified on semi-preparative scale.
制备了三种新型的两性离子氧杂环盐:3-
十二烷基-5-乙基-7,8,10-三甲基异氧杂环盐酸盐(
1c)、1-
十二烷基-5-乙基-3-甲基氧杂环盐酸盐(
2b)和3-
十二烷基-5-乙基-1-甲基氧杂环盐酸盐(
2c)。在
十二烷基硫酸钠(
SDS)、
十六烷基三甲基溴化铵硝酸盐(CTANO
3)和Brij 35的胶束中,研究了它们在
过氧化氢氧化
硫苯的催化活性。反应速率强烈依赖于催化剂结构、胶束类型和pH值。氧杂环盐
2比异氧杂环盐
1更有效的催化剂。由于胶束催化的贡献,
vcat/
v0催化和非催化反应速率的比值几乎为80,当盐
2b溶解在CTANO
3胶束中时。然而,在CTANO
3胶束中,非两性离子5-乙基-1,3-二甲基氧杂环盐酸盐(
2a)表现出最高的加速作用(
vcat/
v0=134)。在这种情况下,盐
2a可能作为相转移催化剂,将
过氧化氢从
水相带入胶束内部。研究的催化系统的合成适用性在半制备规模上得到验证。