Stereo‐ and Enantioselective Synthesis of Both cis‐Chrysanthemic Acid Methyl Esters in High Optical Purity

Photochemical strategies for the construction of polycyclic molecules

“…The initial cycloadducts rearrange directly to cyclooctatetraenes. Irradiation of a mixture of benzene (1) and dimethyl acetylenedicarboxylate (120) led via the ortho cycloadduct 121 to the cyclooctatetraene 122 (eq 19).7a…”

Pyrethroid insecticides Chapter IVb. Selected transformations of chrysanthemic acid and its lower esters to Pyrethroid. Use of the Wittig and related reactions

“…Dehydration of the corresponding methyl ester proved to be extremely difficult owing the location of the hydroxyl group on the cyclopropyl carbinyl [Ce]-carbon, well known to be prone to favor the cyclopropane ring opening instead of the β-elimination reaction especially in acidic media leading among others to (23H) (R 1 = R 2 = Me, R= H, Scheme 24, entry b) (Chapter IVa, Section 5.3.1). 12,113,63 Successful synthesis of methyl (1R)-cis-chrysanthemate has nevertheless been achieved via thermal decomposition of the corresponding thionocarbonate 32Me (1,2,3trichlorobenzene, 140 °C, 0.3 h, 90%, Scheme 47). 113 The latter has been prepared on reaction with an p-tolyl chlorothiocarbonate (ArOC(=S)Cl, pyr., CH2Cl2, 0 °C, 48 h, 80%; Scheme 47) but its reproducibility has been questioned.…”

“…12,113,63 Successful synthesis of methyl (1R)-cis-chrysanthemate has nevertheless been achieved via thermal decomposition of the corresponding thionocarbonate 32Me (1,2,3trichlorobenzene, 140 °C, 0.3 h, 90%, Scheme 47). 113 The latter has been prepared on reaction with an p-tolyl chlorothiocarbonate (ArOC(=S)Cl, pyr., CH2Cl2, 0 °C, 48 h, 80%; Scheme 47) but its reproducibility has been questioned. 113 This is why the β elimination of triphenylphosphine oxide embedded in the Wittig reaction let this reaction unique for the synthesis of chrysanthemic esters and analogues.…”

“…113 The latter has been prepared on reaction with an p-tolyl chlorothiocarbonate (ArOC(=S)Cl, pyr., CH2Cl2, 0 °C, 48 h, 80%; Scheme 47) but its reproducibility has been questioned. 113 This is why the β elimination of triphenylphosphine oxide embedded in the Wittig reaction let this reaction unique for the synthesis of chrysanthemic esters and analogues. Scheme 47.…”