Synthesis of (7E,9Z)-7,9-dodecadien-1-yl acetate, a sex pheromone of lobesia botrana

All four stereoisomers (7-10) of ethyl undeca-2,4-dienoate were prepared in ≥98% isomeric purity by Pd-catalyzed alkenylation (Negishi coupling) using ethyl (E)-and (Z)-β-bromoacrylates. Although the stereoisomeric purity of the 2Z,4E-isomer (8) prepared by Suzuki coupling using conventional alkoxide and carbonate bases was ≤95%, as reported earlier, the use of CsF or n Bu4NF as a promoter base has now been found to give all of 7-10 in ≥98% selectivity. Other widely known methods reveal considerable limitations. Heck alkenylation was satisfactory for the syntheses of the 2E,4E and 2E,4Z isomers of ≥98% purity, but the purity of the 2Z,4E isomer was ≤95%. Mutually complementary HornerWadsworth-Emmons and Still-Gennari (SG) olefinations are also of considerably limited scopes. Neither 2E,4Z nor 2Z,4Z isomer is readily prepared in ≥90% selectivity. In addition to (2Z,4E)-dienoic esters, some (2Z,4E,6E)-and (2Z,4E,6Z)-trienoic esters have been prepared in ≥98% selectivity by a newly devised Pd-catalyzed alkenylation-SG olefination tandem process. As models for conjugated higher oligoenoic esters, all eight stereoisomers for ethyl trideca-2,4,6-trienoate (23-30) have been prepared in ≥98% overall selectivity.highly selective synthesis | Pd-catalyzed Negishi coupling A lkenes represent a large number of natural products of bioactive and medicinally important compounds. Of interest in this study are those containing conjugated dienes and oligoenes (1-11) (Fig. 1). Among numerous known methods for the syntheses of alkenes including conjugated dienes and oligoenes (12, 13), carbonyl olefination reactions, notably Wittig olefination (14) and its variants, such as Horner-Wadsworth-Emmons (HWE hereafter) (15, 16), and Still-Gennari (SG hereafter) (17) as well as Ando (18) modifications have been widely used along with related Si-promoted (Peterson) (19) and S-promoted (Julia and Paris) (20) olefination reactions. As useful as these reactions are, they often lack very high (≥98%) stereoselectivity.In search for highly (≥98%) stereoselective alkene synthesis methodology, our attention was initially drawn to alkyne hydroboration, which generally proceeds in >99% syn-selectivity. Following some promising leads of Brown (21) and Zweifel and co-workers (22-25), we reported in 1973 a couple of highly selective routes to 1,4-disubstituted (E,E)-and (E,Z)-1,3-dienes (1, 3, 26), which appear to represent the earliest syntheses of unsymmetrically substituted conjugated dienes in very high (≥97%) selectivity via organometallic alkenylation.Despite highly selective and satisfactory results described above, our continued search for a more generally applicable and straightforward route to conjugated di-and oligoenes led to the discovery in 1976 of the Pd-catalyzed alkenyl-alkenyl coupling with alkenylalanes (27) and subsequently with alkenyl derivatives containing Zr (28) and Zn (29), collectively known as Negishi coupling (30,31). Along with the subsequently developed alkenylboron version (Suzuki coupling) (32-34), the Pd-catalyzed alken...

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“…Of interest in this study are those containing conjugated dienes and oligoenes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11) (Fig. 1).…”

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confidence: 99%

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

Wang

Mohan

Negishi

2011

Proc. Natl. Acad. Sci. U.S.A.

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“…This second route (Scheme 2) utilizes a different orthoester Claisen rearrangement and is preferred over Scheme 1 since it could be modestly scaled up for field tests. While the second route is similar to the work done by Labovitz et al, 6 it is shorter and the reduction conditions employed afford a single isomer as opposed to small amounts of the undesired E,E-isomer.…”

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confidence: 75%

Synthesis of (9E,11Z)-Hexadeca-9,11-dienal, Sex Pheromoneof the Pecan Nut Casebearer,Acrobasis nuxvorella(Neunzig)

Passaro¹,

Webster²

2003

Synthesis

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“…Allylic nonconjugated enynols have been rearranged (206,217,223) to prepare mixtures of E and Z conjugated enynes, which can be separated prior to further reaction, or as in one case (223) treated with the alkyl lithium reagent (486) in the presence of dilithium tetrachlorocuprate to give an E-enyne (Scheme 86). Conjugated enynes have also been prepared by dehydration of \t-ynols (202,213,217,224), by Wittig reaction (213), via vinyl copper intermediates (225) (Scheme 87), and from alkenyl boranes (see below).…”

Section: Scheme 85mentioning

confidence: 99%

“…Conjugated enynes have also been prepared by dehydration of \t-ynols (202,213,217,224), by Wittig reaction (213), via vinyl copper intermediates (225) (Scheme 87), and from alkenyl boranes (see below). The acetylene can be reduced to a Zolefin with Lindlar catalyst (213,217,226) or preferably via hydroboration-protonolysis (223,224,227), or to an E-olefin with lithium aluminium hydride (225).…”

Section: Scheme 85mentioning

confidence: 99%

Insect Pheromones: A Critical Review of Recent Advances in Their Chemistry, Biology, and Application

Brand

Young²,

Silverstein

1979

Fortschritte Der Chemie Organischer Naturstoffe / Progress in the Chemistry of Organic Natural Products

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Synthesis of (7E,9Z)-7,9-dodecadien-1-yl acetate, a sex pheromone of lobesia botrana

Cited by 25 publications

References 6 publications

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

Highly selective synthesis of conjugated dienoic and trienoic esters via alkyne elementometalation–Pd-catalyzed cross-coupling

Synthesis of (9E,11Z)-Hexadeca-9,11-dienal, Sex Pheromoneof the Pecan Nut Casebearer,Acrobasis nuxvorella(Neunzig)

Insect Pheromones: A Critical Review of Recent Advances in Their Chemistry, Biology, and Application

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