Development of Polymer-Supported π-Acid Catalyst

(1) 2-（4-乙烯基苄基）-丙烷- 1,3 -二醇(1)与四氰乙烯（TCNE）结合，生成带有苯乙烯部分的二氰烯缩醛（DCKA）(2)，与乙二醇二甲基丙烯酸酯（EGDMA）聚合，得到聚合物负载的DCKA（聚DCKA）(3)，为粉末，不溶于普通溶剂。(2)在与底物等量0.2的条件下，聚dcka(3)在60℃的MeCN中可有效催化芳香、饱和和α、β-不饱和醛和酮类的二甲基缩醛与硅基型碳亲核试剂TMS-CN和Ar-C (=CH_2) O-TMS的mukaiyama型缩醛缩合反应。(3)聚dcka(3)能在60℃下有效催化亚胺与酮、酯烯醇基醚的Mannich反应。催化剂(3)在醛、胺和硅基型碳亲核试剂存在下只促进三组分曼尼希反应。(4)聚dcka(3)可催化醇类、醛类和酮类的缩醛型保护基团的脱保护反应和醇类的硅醚的化学选择性脱保护反应。特别是在水条件下（MeCN/水混合溶剂和仅水）的脱乙醛反应中，对催化剂(3)、二氰烯酮缩醛和单体DCKA(2)的活性进行了测试，发现聚DCKA(3)具有显著的正聚合效应。(5)在上述(2)、(3)、(4)的反应中，聚合物催化剂(3)很容易从混合物中回收，并且可以多次重复使用而不损失活性。

(1) A combination of 2-(4-vinylbenzyl)-propane-1, 3-diol (1) and tetracyanoethylene (TCNE) led to formation of a dicyanoketene acetal (DCKA) (2) bearing the styrene moiety in the molecule, which was polymerized with ethyleneglycol dimethacrylate (EGDMA) to produce a polymer-supported DCKA (poly-DCKA)(3) as a powder insoluble in the common solvents.(2) In a amount of 0.2 equiv. to the substrates, poly-DCKA (3) was found to catalyze effectively the Mukaiyama-type aldol condensation reactions of dimethyl acetals of aromatic, saturated, and α, β-unsaturated aldehydes and ketones with silyl-type carbon nucleophiles such as TMS-CN and Ar-C (=CH_2) O-TMS at 60 ℃ in MeCN.(3) Poly-DCKA (3) was found to catalyze effectively the Mannich reaction of imines with enolsilyl ethers of ketones aud esters at 60 ℃ in MeCN.The catalyst (3) promoted exclusively the three component Mannich reaction in the presence of an aldehyde, an amine, and a silyl-type carbon nucleophile.(4) Poly-DCKA (3) was found to catalyze deprotection reactions of acetal-type protecting groups of alcohols, aldehydes, and ketones and chemoselective deprotection of silyl ethers of alcohols. Particularly in the deacetalization recations under aqueous conditions (MeCN/water mixed solvent and water only) a remarkable positive polymer effect of poly-DCKA (3) was observed in the examination of acitivity of catalysts, (3), dicyanoketene ethylene acetal, and monomeric DCKA (2).(5) The polymeric catalysts (3) was recovered easily from the mixtures in the reactions mentioned above ((2), (3), (4)) and could be reused several times without any loss of activities.