报道了新的有机可溶性路易斯酸性多金属氧酸盐(POMs)的制备。这些络合物是通过将Zr,Sc和Y原子掺入相应的单腔道森[P 2 W 17 O 61 ] 10-和Keggin [PW 11 O 39 ] 7-多氧钨酸盐制备的。评价了这些化合物对C的催化活性。Diels-Alder,Mannich和Mukaiyama型反应中的C键形成。报道了与先前描述的路易斯酸性POM的比较。亚胺和醛之间或各种亚胺之间的竞争性反应表明,通过改变掺入聚阴离子骨架中的金属原子,可以实现反应性的精细调节。一系列使用吡啶衍生物的实验使我们能够区分POM的Lewis酸度和诱导的Brønsted酸度。这些催化剂以路易斯酸性方式活化亚胺,而醛通过间接布朗斯台德催化剂活化。
N-Allylideneamines 1a, b were prepared from acrolein and diphenylethyl or trityl amine in the presence of Ti(OEt)4. Double nucleophilicaddition of various ketene silyl (thio)acetals and trimethylsilyl cyanide to these imines proceeded efficiently to give, after workup with TFA, homoglutamic acid derivatives 3 and valerolactam 5.
In the presence of silica gel or titanium tetrachloride, ketenesilylacetals or ketenesilyl thioacetals underwent 1,4-addition with α,β unsaturated aldimines which possess a large triphenylmethyl group at the imino nitrogens followed by reduction with sodium cyanoborohydride to give aminopropylated products, δ-amino esters, in good yields.
Treatment of silyl enol ethers of various carbonylcompounds with Et2Zn and fluoroalkyl halides (Rf–X) in the presence of RhCl(PPh3)3 in DME gave the corresponding α-Rf carbonylcompounds. A highlyreactive alkyl-rhodium complex which was derived from RhCl(PPh3)3 and Et2Zn must be crucial in this reaction by accelerating the reaction rate and improving the yields dramatically. This reaction overcomes
在RhME(PPh 3)3存在下,在DME中用Et 2 Zn和氟代烷基卤化物(R f –X)处理各种羰基化合物的甲硅烷基烯醇醚,得到相应的α- Rf羰基化合物。衍生自RhCl(PPh 3)3和Et 2 Zn的高反应性烷基铑络合物必须通过加快反应速率和显着提高产率来在该反应中发挥关键作用。该反应克服了由于R f –X的反极化而在合成α- Rf羰基化合物时遇到的困难。