Ruthenium‐Catalyzed Metathesis of Conjugated Polyenes

Abstract

Abstract:In the past decade numerous examples of olefin metathesis-based chemical technologies have been developed making olefin metathesis increasingly dominant in several sustainable and green chemical processes. In spite of the wide application profile, conjugated olefin metathesis -especially conjugated polyene metathesis -is an area of great interest with little exploration. Metathesis of conjugated polyenes is often cumbersome and requires high catalyst loading, most probably due to formation of less or inactive ruthenium  3 -vinylcarbene intermediates. Mechanistic understanding and development of a new highly active catalytic system for olefin metathesis will open new areas for exploration. For example, the utilization of petrochemical by products such as cyclopentadiene or a new way in utilizing butadiene, isoprene and conjugated electron systems containing natural products such as terpenes and polyunsaturated fatty acids. Understanding the mechanism of ruthenium  1 - 3 -vinylcarbene interconversion may open the way to the development of new generation ruthenium-based latent metathesis catalyst systems. This review summarizes the most relevant pioneer work focused on metathesis of conjugated polyenes in order to open new ideas for the development of forthcoming latent metathesis catalysts and to explore different application areas.

One‐pot Synthesis of 1,3‐Butadiene and 1,6‐Hexanediol Derivatives from Cyclopentadiene (CPD) via Tandem Olefin Metathesis Reactions

“…This is not surprising as CPD is relatively unstable, it can spontaneously dimerize to DCPD via Diels‐Alder (DA) reaction ,. In addition, the conjugated electron system is expected to reduce activity in metathesis reactions via the formation of less or non‐reactive η 4 ‐allylidene (vinylcarbene) species (Scheme ) …”

Transformations of bio‐sourced 4‐hydroxyphenylpropanoids based on olefin metathesis

“…Cross metathesis involving a conjugated diene as partner has not been studied extensively as compared to monoolefins. [54] However, the cross metathesis of terminal olefins with methyl (2Z,4E)-hexadienoate (77) has been shown to selectively involve its 4,5 double bond leading to the formal introduction of a new substituent at C5. When equimolar amounts of (2) and (77), (78) or (79) were treated in dichloromethane at 40°C for 8 h in the presence of 5 mol% of Ru2, the new dienes (80)- (82) were produced in about 70 % yield as pure stereoisomers together with small amounts of the selfmetathesis product of (2) (Scheme 20).…”

Preparation of cubic-shaped sorafenib-loaded nanocomposite using well-defined poly(vinyl alcohol alt-propenylene) copolymer

“…Nevertheless, ruthenium metathesis catalysts are rendering high functional group tolerances. (Balla et al, 2016) Earlier studies reported the ruthenium catalyzed ROMP of hydroxyl functionalized cyclooctene resulting in linear hydroxyl-functionalized polyoctenamers. (Hillmyer et al, 1995) The synthesis of welldefined ethylene-vinyl alcohol copolymers was reported by the ADMET of two vinyl acetate-containing symmetrical -diene monomers (Li et al, 2013) and also introduced primary, secondary and tertiary hydroxyl groups in precise intervals into the polyolefin chain.…”