Study On Cyclocompounds By α,α-dicyanoalkenes

a,a-Dicyanoalkenes are nucleophile. The acidity of y-C-H is greatly enhanced owning to the strongly electron-withdrawing groups which attached to the C=C bond. Moreover, a,a-dicyanoalkenes are potential successful electrophiles in synthetic chemistry. This dissertation studied from two parts. The first part was about an extremely facile and mild synthesis of trisubstituted2,3-dihydroisoxazoles,2-cyano-3-aryl-acrylamides and2-cyanobut-2-enoic acid derivatives. The second part was on organocatalytic asymmetric Michael addition reactions for synthesis of chiral multi-functionalized polyheterocyclic benzopyran derivatives.In the current work, we have developed an extremely facile and mild synthesis of trisubstituted2,3-dihydroisoxazoles, including spirocyclic compounds that are potentially relevant to natural product synthesis, by the reaction of hydroxylamine with a,a-dicyanoalkenes at pH-10with an unexpected ring-opening of2,3-dihydroisoxazoles to afford2-cyano-3-aryl-acrylamides and2-cyanobut-2-enoic acid derivatives. The reaction undergo the Michael addition, then following intramolecular cyclization, and the nucleophilic addition of the hydroxyl and cyano group on the moiety, then proton transfer. We got the functionalized2,3-dihydroisoxazoles. In addition, an unexpected ring-opening has been studied as well.2,3-dihydroisoxazoles were protonated, then followed by a single electron-transfer (SET) mechanism. We also studied one-pot synthesis of open-ring products.(i)The scope of the domino reactions was quite broad and good to excellent yields were obtained.(ii)The reactions can be carried out in water as a cheap and environmentally benign solvent, and a simple purification step provides.(iii)The method for the synthesis of trisubstituted2,3-dihydroisoxazoles can be conducted on a larger scale (>10g) at low cost making it an ideal alternative to existing methods.Next, chiral multi-functionalized polyheterocyclic benzopyran derivatives were prepared based on the development of an organocatalytic enantioselective domino reaction of a,a-dicyanoolefins with3-nitro-2H-chromenes. The reaction undergo the Michael addition, then following intramolecular cyclization, then proton transfer. We got the chiral multi-functionalized polyheterocyclic benzopyran derivatives. Notably, the designed reactions are highly regio-, chemo-, diastereo-, and enantio-selective, which simultaneously give the desired multifunctional products with up to four vicinal chiral carbon centers. In particular, the asymmetric organocatalytic cascade reactions processes operational simplicity, environment friendliness, and rapid one-pot entries to molecular complexity via atom, step and redox economic or protecting group-free protocols.