The Research Of Direct Aldol Reaction Catalyzed By Pyrrolidine/acid Bifunctional Organocatalyst And Method For Selectively Removed The MOM-ethers By PPh₃/CBr₄

This thesis has explored the influence of acidity on the direct aldol reactions catalyzed by pyrrolidine/acid bifunctional organocatalyst. It was found that the match of the acidity and basicity is very important to obtain good reactivity and high yield in the pyrrolidine/acid bifunctional organocatalyst system. It has proved that the combination of pyrrolidine/p-nitrophenol is a high efficiency catalyst, and employed in the direct aldol reaction of aldehydes and ketones. Existance of moderate amount of water is benefit for the synthesis of mono-aldol products. It was found that double-aldol products could be obtained catalyzed by pyrrolidine/phenol under the optimal conditions. Our research may give some help for the design of high efficient new organic catalysts. In order to find more mild and efficient catalytic system, we have studied the influence of the pyrrolidine/multi-phenol on the reactivity and chemoselectivity. It was found that the double-hydrogen-bond and a small amount of water are very important to obtain good reactivity and high yield. The pyrrolidine/catechol bifunctional catalyst system, which utilizes inexpensive chemicals and does not require preactivation of the donor and the acceptor, could activate the Aldol reaction to proceed smoothly under mild reaction conditions in short times. We also have set up a mild and efficient method for the selective removal of MOM ether group in the presence of other protective groups using CBr₄ and PPh₃ in an aprotic solvent (CH₂ClCH₂Cl) at 40℃. The adopted procedure is simple, inexpensive and high yield that makes it a useful addition to the existing methods.