#### Dehydrative allylation and cyclization catalyzed by palladium-briphos complexes = 팔라듐 브리포스 착화합물의 탈수 알릴 치환 반응 및 고리화 반응 연구

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The efficient and atom economical synthetic methods are highly desirable in the field of synthetic chemistry. For this reason, metal catalyzed reactions have been developed by many researchers for making carbon-carbon bond or carbon-hetero atom bond forming reactions. These reactions are used to synthesize natural products and bioactive molecules. The reported transition metal catalyzed coupling reactions generally experience some synthetic problems such as moisture sensitivity or poor functional group tolerance. To overcome these challenges, more atom-economical coupling reactions are required. Especially, the direct activation of hydroxyl groups is attractive because the coupling reaction generates water as the only byproduct. However, allylic alcohols were barely used for allylation reactions because hydroxyl functional group is known as a poor leaving group. Despite much efforts, the transition metal catalyzed dehydrative allylic substitution is a challenging reaction. In order to develop the dehydrative allylic substitution between allyl alcohol and N-heterocycles, the palladium-briphos system has been investigated. We used the briphos ligand for the reaction, which can activate the hydroxyl groups because of good $\pi$-acceptor properties. The briphos ligand developed in this group and shows a new structure and enhanced reactivity. In addition, it can be easily prepared at very high yields in only two steps. With various primary amine starting materials, various substituents can be easily introduced in the ligand structure. The experimental results showed that a briphos ligand together with $Pd(dba)_2$ is a highly efficient catalyst, and an acid additive involved in the rate-determining step promotes the catalytic cycle. The coupling reaction of allyl alcohols with N-heterocycles including imidazoles, benzimidazoles, and triazoles proceeded under mild reaction conditions with high yields using Pd/briphos and pentafluorophenol. The dehydrative cyclization by using palladium-briphos catalysis has been investigated. N-heterocycles are used in small molecule imaging technologies such as protein and DNA labeling, catalysis, molecular recognition, pharmaceuticals. Therefore, N-heterocyclization reaction has been developed mainly by using various metal catalysts. Cyclic molecules of various shapes are generally synthesized with low yields. We have studied the dehydrative cyclization as an application from dehydrative allylic substitution by palladium-briphos catalysis. Two-consecutive substitution reactions were conducted with 1,4-dihydroxy-1,2-butene that can mediate two allylic substitution at the C1 and C4 positions. The nucleophile was also selected so that the two nitrogen heteroatoms are connected to each other through carbon linkage to enable double substitution. After the first substitution, the second substitution also proceeds to the reaction site via the $\pi$-allyl-metal complex, an intermediate of the allylic substitution reaction, which results in the formation of a large ring form with four carbons. It was confirmed that even with long diamine nucleophiles in chain form, the synthesis was achieved with high yields.
Kim, Hyunwooresearcher김현우researcher
Description
한국과학기술원 :화학과,
Publisher
한국과학기술원
Issue Date
2018
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 화학과, 2018.8,[i, 115 p. :]

Keywords

URI
http://hdl.handle.net/10203/265454