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Cyclic enones, reductive coupling with

A total synthesis of functionalized 8,14-seco steroids with five- and six-membered D rings has been developed (467). The synthesis is based on the transformation of (S)-carvone into a steroidal AB ring moiety with a side chain at C(9), which allows the creation of a nitrile oxide at this position. The nitrile oxides are coupled with cyclic enones or enol derivatives of 1,3-diketones, and reductive cleavage of the obtained cycloadducts give the desired products. The formation of a twelve-membered ring compound has been reported in the cycloaddition of one of the nitrile oxides with cyclopentenone and as the result of an intramolecular ene reaction, followed by retro-aldol reaction. [Pg.92]

DIBAL-H/n-butyllithium, in cyclic and acyclic systems with iron pentacarbonyl, in cyclodecanes with lithium dihydrodimethoxyaluminate(III)/copper(I) iodide, and in cyclohexane and cyclopentane systems with NaH/sodium r-butylpentyl/Ni(OAc)2. ° The monoreduction of 1,3-diketones can be carried out under similar conditions, as illustrated by the reaction of a substituted cyclohexane-1,3-dione with oxalyl chloride to give the corresponding 1-chlorocyclohexenone, which was subsequently reduced to the enone with zinc-silver couple (Scheme 45). Kropp et al. have reported the photolytic reduction of vinyl iodides in acyclic systems however, when an a-hydrogen is present, formation of the diene product is a limiting side reaction (Scheme 46). For a more extensive discussion of vinyl halide reductions, see the preceding chapter in this volume. [Pg.938]

The nickel-catalyzed reductive coupling reaction of methyl vinyl ketone with enyne 43 bearing a P-dicarbonyl moiety proceeds with liberation of the P-dicarbonyl enolate (Scheme 5.56) [39]. Reductive coupling of 43 with enone would afford nickelaoxacyclooctadiene 44. Transmetalation is accompanied by carbonickelation to yield 45. Intermediate 45 engages in P-carbon elimination through a six-membered cyclic transition state to liberate nickel enolate 46, which should be transformed to the corresponding zinc enolate to complete the catalytic cycle, and zinc enolate 47, which is eventually protonated upon hydrolysis. [Pg.188]


See other pages where Cyclic enones, reductive coupling with is mentioned: [Pg.276]    [Pg.284]    [Pg.173]    [Pg.110]    [Pg.89]    [Pg.163]    [Pg.88]    [Pg.209]    [Pg.344]    [Pg.1971]    [Pg.285]   
See also in sourсe #XX -- [ Pg.163 ]




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Enone reduction

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Reduction Reductive coupling

Reduction couple

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