Part I: N-heterocyclic carbene catalyzed homoenolate addition of enals to nitroalkenes. Part II: Palladium catalyzed N-heterocyclic glycosides synthesis

• Main Author: Ji, Li
• Other Authors: Liu Xuewei
• Format: Theses and Dissertations
• Language: English
• Published: 2015
• Subjects: DRNTU::Science
• Online Access: http://hdl.handle.net/10356/62906
• Institution: Nanyang Technological University

Part 1. N-heterocyclic carbene catalyzed highly diastereoselective and potentially multifunctional nitroester from α,β-unsaturated aldehyde and nitrodiene is described. Amongst the imidazolium carbene catalysts tested, sterically demanding 1,3-bis(2,6-diisopropyl phenyl)imidazolium chloride gave the best chemical yield and diastereoselectivity. A variety of aryl substituted cinnamaldehyde derivatives undergo smooth addition with aryl substituted nitrodiene to afford five carbon synthon frameworks with additional C=C double bond. To demonstrate the utility of this methodology, a few applications such as cyclopentanol and tetra- and trisubstituted tetraline derivatives were synthesized from the multifunctional nitroester. Furthermore, we have developed a chiral version of the homoenolate addition to nitroalkenes for the construction of highly enantio-enriched “5-carbon synthon” nitroester by using a chiral N-heterocyclic carbene catalyst. Various types of enals and nitroalkenes were well tolerated with the reaction conditions to afford the desired δ–nitroesters in excellent enantioselectivities. Part 2. An efficient and highly stereoselective strategy for the synthesis of N-heterocyclic glycosides was developed. This method is based on a palladium catalyzed allylation, which allows formation of N-heterocyclic glycosyl linkages in moderate to good yields with excellent β-selectivity. The utility of this method was further demonstrated by expedient syntheses of bis-indole sugars that have potential as antiproliferative drugs from N-glycosyl isatine products.