3- Alkyl-1,2-cyclohexanediones

ALKYLATION OF DIMEDONE WITH A TRICARBONYL(DIENE)IRON COMPLEX TRlCARBONYL[2-[(2,3,4,5-t))-4-METHOXY 2,4 CYCLOHEXADUEN-l-YLJ-5,5-DIMETHYL-l,3-CYCLOHEXANEDIONE]IRON... 

Another procedure relies on a domino Michael-O-alkylation reaction sequence to yield a variety of dihydrofurans. Combination of cyclohexanedione (30) with vinyl bromide 50 in the presence of l,8-diazabicyclo[5.4.0]undec-7-ene (DBU) provides dihydrofuran 51 in 83% yield. Numerous 1,3-dicarbonyls and vinyl bromides are amenable to this methodology, and thus a wide range of products like 51 are available via this strategy. 

The present procedure is simpler than others previously described and gives equally good yields. It is easily adapted to the preparation of large quantities of either the diester or the diketone. It can be extended to the preparation of various alkylated 1,4-cyclohexanediones and bicyclic diketbdicarboxylic esters such as diethyl bicyclo[2.2.2]octane-2,5-dione-l,4-dicar-boxylate. 1,4-Cyclohexanedione is a useful intermediate for... 

On the basis of these findings, a pathway for this cydoaddition is proposed in Scheme 7.24. The first step is the nucleophilic attack of the carbon atom in the 2-position of 1,3-cyclohexanedione on the Cy atom of the allenylidene complex to give a vinylidene complex, which is transformed into an alkenyl complex by intramolecular nucleophilic attack of the oxygen atom of a hydroxy group of an enol on the C, atom of the vinylidene complex. By the use of Ic with its bulkier alkanethio moiety as a catalyst and at lower temperature, a subsequent intramolecular cyclization may be slow enough to make isolation of the alkylated product possible. 

ALKYLATION OF DIMEDONE WITH A TRICAEBONYL(DIENE)IEON COMPLEX TRICAEB0NYL[2-[(2,8,4,5-7,)-4-METH0XY-2,4-CYCL0HEXADIEN-1-YLJ-5,5-DIMETHYL-I,3-CYCLOHEXANEDIONE]IEON... 

In an application of the Niki reaction,474 the alkylation of 1,3-cyclohexanedione with trans-1,4-dibromo-2-methyl-2-butene (a reaction previously mentioned in connection with compound 218 (Section IV,A,3,c,iv) leads to a similar product, without methyl groups in position 6.721... 

Rearrangement ofl,2-dialkyl- y3-cyclohexanediones.1 Reaction of these substrates with the anion (LDA) of this phosphonate results in rearrangement to 3-alkyl-2-cyclohexenones in 60-93% yield. Addition of ClSi(CH3)3 improves the yield. The... 

Cyclopentanedione and 1,3-cyclohexanedione are highly enolized ketones. Will they give the same proportions of O- and C-alkylations under the same reaction conditions (of solvent, cation, etc.) ... 

Baylis-Hillman acetates have been conveniently transformed into tri/tetracyclic heterocyclic frameworks containing an azocine moiety via a one-pot multistep protocol involving alkylation, reduction, and cyclization sequence <2007OL2453>. Treatment of Baylis-Hillman acetate 284 with 1,3-cyclohexanedione in the presence of K2CC>3, followed by treatment of the resulting product with Fe/AcOH, gave 77% fused azocine 285 (Scheme 119). 

Alkylations of nitrophenylacetates, indole, and methyl benzylidene glycinate under dry conditions induced by microwaves have been studied, leading to the synthesis of arenes (66) linked by a long hydrocarbon chain (Abramovitch et al., 1995). Kumar et al. (1999) reported the enviromnental-friendly process for the synthesis of 2-alkylated hydroquinones (67) under microwave irradiation using 1,4-cyclohexanedione and aldehydes catalyzed by KF-AI2O3. An attractive methodology using microwave irradiation is described by Vanelle et al. (1999) for reactions of... 

The addition of ethyl sodiomalonate to olefinic ketones followed by ring closure and /3-keto ester cleavage leads to 1,3-cyclohexanediones. The reaction has been applied to the formation of 2-alkyl-5-phenyl-1,3-cyclohexanediones and is typified by the preparation of 5,5-dimethyl-1,3-cyclohexanedione (85%). Other cyclizations for formation of four-and five-membered rings have been described. ... 

In general, there is significant competition between C- and O-alkylation when the equilibrium concentration of the enol tautomer is relatively high, as in the case of 1,3-cyclohexanedione. ... 

Dianions derived from 1,2-cyclohexanediones react with aldehydes rather stereoselectively, as shown in equation (64). The anti.syn ratio of about 8 1 was shown to be kinetic rather than thermodynamic in nature, and was found to be independent of the alkyl group at C-3. The anti stereoselectivity is even higher with a-branched aldehydes (e.g. >99 1 with isobutyraldehyde). 

In a specific work, it has been shown that chemical modification of hyperforin by acylation, oxidation and alkylation produce detrimental effects on the molecule activity as inhibitor of serotonin uptake [89], and the presence of the enolized cyclohexanedione moiety in its structure has been related to its efficacy on the re-uptake of neurotransmitters. 

Cyclohexanedione is also readily alkylated at position 2, and the alkyl derivatives formed can be cleaved hydrolytically to <5-oxo carboxylic acids by alkali. Stetter has reviewed403 the syntheses carried out by himself and his colleagues by this method. 

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