ChemInform Abstract: Synthesis of 2‐Acyl‐4‐hydroxy‐1,3‐cyclohexanediones.

Abstract

Several pathways leading to the formation of the 2‐butanoyl‐4‐hydroxy‐1,3‐cyclohexanedione (IV) are described.

Chemistry of 2-Acylcycloalkane-1,3-diones

“…Ionic hydrogenation of enol methylates, as well as of β-triketones, , represents a useful procedure for acyl carbonyl group reduction, giving 2-alkyl-substituted enol methylates ( 50 ) in high yields in the case of methyl ethers ( 26 ) (Scheme ).

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“…Methyl enol ethers are used as protective groups for the triacylmethane group in oxidation processes. This is documented by the regioselective 4-hydroxylation of the ether ( 26 ) by lead tetraacetate, tert -butylhypochlorite−silver acetate, or m -chloroperoxybenzoic acid, leading to compound 51 and useful for the synthesis of the widely occurring natural 4-hydroxylated β-triketones (Scheme ) …”

Ionic and Organometallic‐Catalyzed Organosilane Reductions

“…395,441 A similar reduction is seen with the β-methoxy-and β-chloro analogs. 396 The γ -(carboxyethyl)cyclohexenone 80 is fully reduced to the methylene derivative (Eq. 270).…”

“…215 in high yield (>94%), but with formation of approximately equal amounts of the two possible diastereomers formed from the creation of a new chiral center 396. …”

Triethylsilane-Trifluoroacetic Acid

“…12 Addition of a catalytic amount of LiClO 4 or Boron Trifluoride Etherate to the reaction mixture permits regioselective reduction of the side chain carbonyl group even in polyfunctional enones (eq 6). 13 Many aldehydes and ketones react to give symmetrical ethers in the absence of external Avoid Skin Contact with All Reagents alcohols 14 and unsymmetrical ether products when the reductions are run in the presence of added alcohols (eq 7). 15 Reduction of α,β-unsaturated ketones using a ketone:silane:acid ratio; = 1:1:10 gives products with the C=C bond reduced, whereas changing the ratio to 1:3:10 gives products with both the C=C and C=O bonds reduced (eq 8 Reduction of O-benzoyl oximes gives O-benzoyl amines (eq 9).…”