Methylcyclopentane-l,2-dione

Methylcyclopentane-l,3-dione has been prepared in 15% yield by the catalytic reduction of 2-mcthylcyclopentane-l,3,5-trione over platinum.2 The present method is based on the original procedure 3 of Panouse and Sannie with improvements as effected by Boyce and Whitehurst4 and the submitters.6... 

A similar reaction occurs with 2-methylcyclopentane-l,3-dione,176 and can be done enantioselectively by using the amino acid L-proline to form an enamine intermediate. The (S)-enantiomer of the product is obtained in high enantiomeric excess.177... 

The retrosynthetic process (Scheme 6.2) involves the following operations i) substitution of the conjugated double bond by an OH group ii) retro-aldol disconnection of the 1,3-C system, and iii) disconnection at the a-position of the resulting 1,4-D system which leads to 2-methylcyclopentane-l,3-dione and an umpoled three-carbon atom fragment. This retrosynthetic process offers, however, only a theoretical scheme which, in practice, presents some difficulties. For example. Table 5.1 gives 2-nitropropene (3) as a possible equivalent of the umpoled C3 fragment, in which case the process in the synthetic direction would be as... 

Cyclopentane reagents used in synthesis are usually derived from cyclopentanone (R.A. Ellison, 1973). Classically they are made by base-catalyzed intramolecular aldol or ester condensations (see also p. 55). An important example is 2-methylcyclopentane-l,3-dione. It is synthesized by intramolecular acylation of diethyl propionylsuccinate dianion followed by saponification and decarboxylation. This cyclization only worked with potassium t-butoxide in boiling xylene (R. Bucourt, 1965). Faster routes to this diketone start with succinic add or its anhydride. A Friedel-Crafts acylation with 2-acetoxy-2-butene in nitrobenzene or with pro-pionyl chloride in nitromethane leads to acylated adducts, which are deacylated in aqueous acids (V.J. Grenda, 1967 L.E. Schick, 1969). A new promising route to substituted cyclopent-2-enones makes use of intermediate 5-nitro-l,3-diones (D. Seebach, 1977). 

The forward synthetic sequence would therefore involve the Michael reaction of 2-methylcyclopentane-l,3-dione with methyl vinyl ketone to give (20), followed by cyclisation to the hydroxyketone (19), and then dehydration to the target molecule (13a). The overall process of addition and cyclisation is known as the Robinson annelation reaction.3 In this preparative example (Expt 7.6) the methyl vinyl ketone is used directly under conditions which minimise its polymerisation 48 it should be noted, however, that many literature examples of the annelation reaction use Mannich bases or the corresponding methiodides as an in situ source of the a, /J-unsaturated carbonyl component (see Section 5.18.2, p. 801). 

Maple Svrup. The typical flavor of maple syrup which originates during the heat concentration of maple sap in the presence of air has also been extensively investigated (70-80). Important sugar-based degradation products present in maple syrup include 3-methylcyclopentane-l,2-dione and 2,5-dimethyl-4-hydroxy-3(2H)-furanone. 

Methylcyclopentane-l,3-dione has found increasing use as an intermediate in the synthesis of steroids.6-12 The method described is the only practicable method available for the preparation of 2-methylcyclopentane-l,3-dione in large amounts. 

Methylcyclopentane-l,2-dione aroma in dilute soln 1 g in 72 mL water ... 

METHYLCYCLOPENTANE-l,2-DIONE see HMB500 METHYl. CYCLOPEXTENOLONE (FCC) see HMB500 METHYLCYCLOPROPANECARBONYLHYDRAZINE see MIV300... 

The known vinyl ketone (11) has been prepared by the route (7)- (8)— (9). The last compound on heating gave (11). Whereas the reaction between (9) and 2-methylcyclopentane-l,3-dione gave (12), the corresponding reaction with (10) gave (13), evidently owing to the benzenesulphenic acid produced in the reaction. 

The dione (41), obtained from 2-methylcyclopentane-l,3-dione, undergoes asymmetric cyclization to yield (42) (82% yield, 86% optical purity) with L-phenylalanine in acetonitrile. Reduction with sodium borohydride to (43) followed by catalytic reduction gave (45) (major product), (46), and, unexpectedly, compound (44)... 

Compound (80), prepared from 2-methylcyclopentane-l,3-dione and methyl 2-chloroacrylate followed by the sequence (76)-> (77)-> (78)- (79) (resolved)— (80), combined with (71) (prepared from m-methoxyphenylstyrene and diborane) to form the seco-steroid (82)/ Acetic anhydride-toluene-p-sulphonic acid then cyclized this stereoselectively to furnish the triacetate (83) which on saponification gave the triol (84). Interestingly, this compound reacted with toluene-p-sulphonic acid in alcohol to produce, by dehydration and change of configuration at C-14, the compound (85), which served as a source of various 8a-oestrone compounds. Compound (84) on treatment with boron trifluoride etherate underwent pinacol transformation in preference to dehydration to yield the ketone (86) this ketone was correlated with the known compound (87). 

Very substantial asymmetric induction at C-13 was found to take place upon condensation of the optically active hydroxy vinyl ketone 4 (R CsHs) with 2-methylcyclopentane-l,3-dione... 

D.68) 2-Cyclopenten-l-one, 2-hydroxy-3-methyl-, 2-hydroxy-3-methylcyclopent-2-en-l-one, 3-methylcyclopent-2-en-2-ol-l-one 80-71-7] 1,2-cyclopentanedione, 3-methyl-, 3-methylcyclopentane-l,2-dione, cyclotene, corylone, maple lactone, nussol [765-70-8] FEMA 2700... 

D.1. Reactions with Nucleophiles. Previously, a jr-allylic palladium complex was generated by reaction of palladium reagents with allylic hydrocarbons prior to reaction with nucleophiles. In the catalytic version of this reaction, an allylic halide or an allylic acetate is used with a palladium(O) reagent. Why use a palladium complex when enolate alkylation is a well-known process (sec. 9.3.A) A typical enolate coupling reaction is the conversion of 2-methylcyclopentane-l,3-dione (373) to the enolate anion by reaction with NaOH, allowing reaction with allyl bromide. Under these conditions only 34% of 374 was obtained. When allyl acetate was used in place of allyl bromide in this reaction and tetra w(triphenylphosphino)palladium was used as a catalyst, a 94% yield of 374 was obtained.224 in this reaction, formation of the Jt-allyl palladium complex facilitated coupling with the nucleophilic enolate derived from 373, which exhibited poor reactivity in the normal enolate alkylation sequence. 

Yields in the Michael condensation for preparation of the triones 13 were improved by operating in aqueous media and omitting basic catalysis.For example, trione 13a was obtained in 88% yield by stirring a mixture of methyl vinyl ketone Ha and 2-methylcyclopentane l,3-dione 12 in water at 20 for 5 days. This Michael condensation is considered to be self-catalyzed by the acidic... 

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