Low Temperature Isomerisation of (Z)-α,β-Unsaturated Esters into their (E)-Isomers by LiTi(OiPr)₄(SPh) and LiSPh

Cis−Trans Isomerization of Organic Molecules and Biomolecules: Implications and Applications

“…Acrylates can undergo cis−trans isomerization via radical processes, − Lewis acids and metal complexes, protic acids, as well as nucleophiles. , Photochemical isomerization of furylacryloylpeptides used in kinetic mesurements of proteolytic enzymes has shown that the acrylate moiety quickly isomerizes in plain day light. Even though the proteolysis takes place at a remote site, acrylate isomerization strongly influences the enzymatic transformation and has to be taken into account when using furylacryloyl substrates, as demonstrated in the case of furylacryloyl peptide 7 (Scheme ) .…”

Synthesis and Properties of Oligocyclopropyl-Containing Natural Products and Model Compounds

“…Oxidation using pyridinium chlorochromate followed by direct homologation provided a separable mixture of E , E -diester 69 and its E,Z -isomer (∼90:10). The unwanted diester could be partially converted to the desired product by a reagent introduced by Hunter et al [LiTi(Oi-Pr) 4 (SPh)] . DiBAl-H reduction and consecutive cyclopropanation under Charette conditions led to diol 62 .…”

“…The unwanted diester could be partially converted to the desired product by a reagent introduced by Hunter et al [LiTi(Oi-Pr) 4 (SPh)]. 77 DiBAl-H reduction and consecutive cyclopropanation under Charette conditions led to diol 62.…”

“…Next, quatercyclopropane 62 was converted to dienoate 70 following a standard procedure (Scheme 11; monoprotection, oxidation, and chain elongation). Again, the diester was formed as a mixture (71%; E,E:E,Z 84:16), however, the isomerization of the unwanted diene was achieved using Hunter's reagent 77 (63%). Reduction and cyclopropanation in the presence of the chiral modifier ent-38 gave compound 71, essentially as a single isomer.…”

Synthesis and stereochemical assignment of methyl 3-(3-hydroxyphenoxy) acrylate via cis-trans photoisomerization

“…The barrier of the isomerization process is lowered when there is conjugation of the carbon-carbon double bond with a heteroatomic -system. 5 The mechanism of acrylate isomerization is dependent on the presence of other compounds in the solution, such as nucleophiles 7 or radicals. 8 The goal of this paper is to report a short synthetic route for the preparation of methyl 3-(3-hydroxyphenoxy) acrylate (2), a new and potential precursor of the natural product 3-(3-hydroxyphenoxy)-2-propenal (1) from Artemisia species.…”