413. Studies in relation to biosynthesis. Part XXXII. Preparation, spectra, and hydrolysis of poly-β-carbonyl compounds

Abstract

Ultraviolet spectra of mono-and di-anions of some linear tri-P-carbonyl compounds and of acetoacetic and 3,5-dioxohexanoic acid are reported and the course of decomposition of these compounds by alkali is described. A new approach to the preparation of poly-P-diketones by ozonolysis of dihydroaromatic compounds is described, leading to a ketal of undecane-2,4,6,8,10pentaone, the first reported derivative of a linear penta-P-ketone. A new explanation is offered for the I' acidic " fission of p-keto-esters.

Nitrenium Ion Azaspirocyclization—Spirodienone Cleavage: A New Synthetic Strategy for the Stereocontrolled Preparation of Highly Substituted Lactams and N‐Hydroxy Lactams.

“…While attempts to generate 30c through insitu reduction of 21 with sodium borohydride gave unsatisfactory results, concentration of the ozonolysis reaction mixture and reduction with LiBH 4 in THF provided the corresponding bis(hydroxymethyl)pyrrolidinone, 40 which because of its polarity, was converted to bis-O-acetate 29 prior to purification. Treatment of hemiacetal 22 with NaBH 4 or LiBH 4 , on the other hand, failed to provide any useful results. Reasoning that a weaker reducing agent might prove selective for the hemiacetal group, without affecting the methyl ester or promoting decomposition, sodium triacetoxyborohydride in acetic acid was evaluated.…”

“…After stirring for 10 min, the biphasic mixture was partitioned between CH 2 Cl 2 (10 mL) and saturated aqueous NaHCO 3 (5 mL). After separation, the aqueous phase was extracted with CH 2 Cl 2 (3 × 10 mL) and the combined organic extracts dried (MgSO 4 …”

“…(Carboethoxymethylene)triphenylphosphorane (687 mg, 1.97 mmol) was then added and the mixture heated at reflux for 2 h. The reaction was then cooled, concentrated under reduced pressure and the resulting oil partitioned between CH 2 Cl 2 (10 mL) and saturated aqueous NH 4 Cl (7 mL). The organic phase was separated and the aqueous portion extracted with CH 2 Cl 2 (3 × 10 mL), The combined organic extracts were dried (Na 2 SO 4 …”

“…Rather than involving a direct oxidation, in this case, Birch reduction of 1 and cleavage of one or both double bonds in the resulting dihydroaromatic compound 2, most commonly through ozonolysis, serves to unmask the latent dicarbonyl system. 4 This two-step protocol is tolerant of a wide range of aryl substituents (R 1 , R 2 ) and has successfully been applied to the synthesis of β-keto esters, 5 ω-formyl esters, 6 malonate esters, 7 β-diketones, 8 β-formyl ketones, 9 and even higher order polyketides. 10 In contrast to cyclohexadienes 2, there are only a handful of accounts documenting the ozonolytic cleavage of 2,5-cyclohexadienones 5, their electron deficient congeners, to form 1,3-dicarbonyl compounds 7 (Scheme 2).…”

Thermochemistry and photochemistry of spiroketals derived from indan-2-one: Stepwise processes versus coarctate fragmentations

“…Ketal 1 was synthesized according to a published procedure [35]. Ketals 2 and 3 were prepared analogously, starting from indan-2-one and propane-1,3-diol and cis -2-butene-1,4-diol, respectively.…”