Acyclic unsaturated hydrides

D-Ribonolactone is a convenient source of chiral cyclopentenones, acyclic structures, and oxacyclic systems, useful intermediates for the synthesis of biologically important molecules. Cyclopentenones derived from ribono-lactone have been employed for the synthesis of prostanoids and carbocyclic nucleosides. The cyclopentenone 280 was synthesized (265) from 2,3-0-cyclohexylidene-D-ribono-1,4-lactone (16b) by a threestep synthesis that involves successive periodate oxidation, glycosylation of the lactol with 2-propanol to give 279, and treatment of 279 with lithium dimethyl methyl-phosphonate. The enantiomer of 280 was prepared from D-mannose by converting it to the corresponding lactone, which was selectively protected at HO-2, HO-3 by acetalization. Likewise, the isopropylidene derivative 282 was obtained (266) via the intermediate unsaturated lactone 281, prepared from 16a. Reduction of 281 with di-tert-butoxy lithium aluminum hydride, followed by mesylation, gave 282. 

The same procedure was applied to several unsaturated nitriles 125, prepared from various acyclic carboxylic esters with a terminal double bond 124. The intermediate carbonylic compound 126 cyclized either during silica gel chromatography, or on sequential treatment with calcium hydride followed by aqueous ammonium chloride. The result was a five- or six-membered cyanocycloalkenone 127 (Scheme 45 and Table 17) <1999JOC2830>. 

However, similar treatment of alkyl-substituted <5,e-unsaturated alkyl-amines with bromine and sodium hydride fails to yield azabicyclohexanes, but unsaturated acyclic products are formed instead. Suitable bulky substituents are thus apparently essential for the satisfactory synthesis of azabicyclohexanes from (5, -unsaturated amines. ... 

IR-6.2.2.3 Unsaturated homonuclear acyclic hydrides IR-6.2.2.4 Homonuclear monocyclic parent hydrides IR-6.2.2.5 Homonuclear polycyclic parent hydrides IR-6.2.3 Boron hydrides... 

Unsaturated acyclic hydrides are not classified as parent hydrides. Because of the hierarchical rules of substitutive nomenclature, the numbering of the double and triple bonds may not be fixed until various groups and modifications have been numbered. (See Section IR-6.4.9 for an example.)... 

Chamberlin and Reich investigated hydride additions to a,3-unsaturated ketones and the correlation of conformational preferences in enones with the ( )/(Z) stereoselectivity in formation of the corresponding enolates. They found that in acyclic systems s-trans enones gave enolates A and s-cis enones gave enolates B (Scheme 15). The reduction of a,3-unsaturated amides with L-selectride gave the same stereochemical results (Scheme 16). ... 

Reduction of a, -unsaturated carbonyl compounds (6, 491 492). The final paper has now been published. In general, )3-5ubstituted cyclohexenones undergo exclusive 1,4-reduction with either Selectride. Acyclic enones generally undergo 1,2-reduction to allylic alcohols. The Selectrides are particularly useful for 1,4-reduction of enoates. Super-Hydride (lithium triethylborohydride) is less useful for this purpose. Unfortunately L-Selectride reduces o./S-acetylenic esters only to propargylic alcohols. 

Flash thermolysis of a series of methylated bicyclo[3,2,0]hept-2-ene-7-ones gave dihydrotolualdehydes and tolualdehydes as the major products. The suggested reaction path involved recyclization of a heptatrienal formed from the p,y-unsaturated bicyclic ketones by sequential [2 + 2]cycloreversion to the acyclic ketene and 1,5-hydride shift. 

Acyclic (ri -diene)iron complexes will give substituted cyclopentanones or y,5-unsaturated aldehydes upon treatment with nucleophiles under carbon monoxide atmosphere (Scheme 4-119). A proposed mechanism involves the addition of the nucleophile at an inner carbon atom of the t) -diene ligand followed by insertion of carbon monoxide. Subsequent protonation provides the unsaturated aldehyde. Alternatively, the acyliron intermediate can undergo carboferration to give an acyliron intermediate. Isomerization via (3-hydride elimination and readdition provides an iron-enolate anion that upon treatment with acid provides the cyclopentanone. ... 

Atkinson, R. S., and R. H. Green 1,5-Hydride Shifts in Acyclic Systems Containing a,p-Unsaturated Ketones and p-Methoxyphenyl Groups. J. Chem. Soc. Perkin I 1974, 394. 

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