Cyclohexane-1,4-dione, reaction with

Cyclohexane-1,2-dione reacts with ethylene glycol (TsOH, benzene, 6 h) to form the diprotected compound. Monoprotected 1,3-oxathiolanes and 1,3-dithiolanes are isolated on reaction under similar conditions with 2-mercaptoethanol and eth-anedithiol, respectively. ... 

Homoenolate Reactivity The ability to generate homoenolates from enals and its application to the preparation of y-butyrolactones 30, through reaction with an aldehyde or aryl trifluoromethyl ketone, was reported independently by Glorius [8], and Bode and Burstein [9] (Scheme 12.4). A sterically demanding NHC catalyst is required to promote reactivity at the d terminus and to prevent competitive benzoin dimerisation. Nair and co-workers have reported a similar spiro-y-lactone formation reaction using cyclic 1,2-diones, including cyclohexane-1,2-dione and substituted isatin derivatives [10]. 

A perhaps more exotic substrate for the Heck reaction is 1,2-cyclohexanedione [25], The reactivity of this molecule under Heck coupling conditions can probably be attributed to its resonance enol form. This reaction is attractive, because the literature contains relatively few examples of the preparation of 3-aryl-l,2-cyclohexane-diones. Yields varied from good to modest when classic heating and electron-rich aryl bromides were used, and reaction times typically ranged from 16 to 48 h. Similar yields were obtained under continuous microwave irradiation with a single-mode microwave reactor for 10 min at 40-50 W (Eq. 11.10) [25],... 

The reaction of the O-alkylated cyclohexan-l,3-diones 73 with p-substituted anilines in the presence of acetic acid is influenced by the nature of R in 73, yielding 4-anilinoxanthones 74 when R = H, but the condensed y-lactams 75 when R = Me (Scheme 51) <00T5947>. 

Nair and co-workers reported the diastereoselective synthesis of spiro y-butyro-lactones from 1,2-dicarbonyls [125]. The authors studied the reaction with 1,2-cyclohexane dione 230 which produces the desired lactone 232 in good yields Eq. 22a. Isatins 233 are more reactive, but the products 235 are obtained as a 1 1 separable mixture of diastereomers Eq. 22b. The Nair research group extended this methodology to include homoenolate addition to tropanone 236 to form bicyclic 5-lactones 238 Eq. 22c [126]. 

The dioxime of cyclohexane-1,4-dione reacts with acetylene in an autoclave in the presence of KOH/dimethyl sulfoxide (DMSO) (Trofimov reaction) to give l,5-divinyl-4,8-dihydropyrrolo[2,32f]indole by sequential [1,3]- and [3,3]-rearrangements in poor yield (Equation 91) <2004TL3789>. 

Dioxo-8a-methyl-l, 2,3,4,6,7,8,8a-octahydronaphthalene has been obtained through the reaction of 2-methyl-l,3-cyclohexane-dione with acetonedicarboxylic acid and formaldehyde,3 4-diethyl-amino-2-butanone methiodide,3 pyridine and 4-diethylamino-2-butanone,4 triethylamine and 4-diethylamino-2-butanone,5 and by cyclization of 2-methyl-2-(3-oxobutyl)-l,3-cyclohexanedione using either aluminum fer/-butoxide or piperidine phosphate as catalyst.6 7... 

The reaction of 1,2-dicarbonyl compounds with amidrazones, semicarbazide, thiosemicarbazide and aminoguanidine has also been used for the synthesis of condensed 1,2,4-triazines. Cyclohexane-, cycloheptane- and cyclooctane-1,2-diones (489) with amidrazones (453) afford the cycloalkatriazines (490) (78HC(33)189, p.66l). 

A nitrile-stabilized carbanion is also involved in a synthesis of a fused pyranone system (81S225). A range of 2-ureidomethylenecyclohexane-l,3-diones, e.g. (308), react with activated acetonitriles in the presence of a strongly basic catalyst to produce 5-oxo-5,6,7,8-tetrahydrocoumarins (309). Since the substrates are readily available from cyclohexane-1,3-diones by reaction with triethyl orthoformate and a urea, the synthesis is attractive (Scheme 88). Furthermore, it has been applied to a pyran-2,4-dione, whereupon the 2,5-dioxopyrano[4,3-6]pyran (310) is formed. 

As an extension of the successful Strecker reaction under high pressure [83], a heterocyclic version of this reaction was investigated by us but met with very limited success. For example, 1 equivalent of 1,2-diacetylbenzene (152) with 1,2-diaminobenzene (153) and TMSCN (2.4 equivalents) afforded 5,6,11,12-tetrahydro-6,11 -dimethyldibenzo[b,f][ 1,4]diazo-cine-6,ll-dicarbonitrile (154), albeit only in 17% yield in one step. A similar reaction of cyclohexane-1,2-dione (155) with 153 produced 1,2,3,4,5,10-hexahydrophenazine-4a,10a-dicarbonitrile (156) in 13% yield along with the aromatized product, 1,2,3,4-tetrahydrophenazine (157) (Scheme 42). However, similar attempts with other diketones, such as 2,5-hexanedione, 2,3-butadiene, and 9,10-phenanthrenequinone, met with failure, either giving a complex mixture of products or well known and commercially available product possessing a pyrazine skeleton [100]. 

Disubstituted cyclopentane-1,3-diones and cyclohexane-1,3-diones were used as substrates. After formation of the aldol adducts subsequent intramolecular dehydration furnished products of types 94 and 96. The asymmetric intramolecular aldol reaction proceeds with a broad variety of natural amino acids as organocata-lysts. Among these L-proline was usually found to be the most versatile. For example, conversion of the 2,2-disubstituted cyclopentane-1,3-dione 93 in the presence of L-proline gave the desired product 94 in 86.6% yield and with enantioselectivity of 84% ee [97]. This example and a related reaction with a 2,2-disubstituted cyclohexane-1,3-dione 95 are shown in Scheme 6.42. Chiral induction depends... 

In the study of a model for the possible synthesis of concentrine, 3,4-dihy-dropapaverine has been condensed with cyclohexane- 1,2-dione in the presence of base (preferably Triton B) to give the spiro-ketone (14). The reaction presumably proceeds via the carbanion (10) and the intermediates (11), (12), and (13). A similar reaction with benzil affords the diphenyl ketone (15). Catalytic reduction of the ketone (14) yields the corresponding alcohol.26... 

Langer and coworkers reported on the [3+ 2]-type C,0-cyclodialkylation of cyclohexane-1,3-dione dianion with l,4-dibromo-2-butene (Scheme 25)39. The formation of the tetrahydrofuran-fused cyclohexenone can be explained by a regioselective attack of the terminal carbon of the dianion on the l,4-dibromo-2-butene and subsequent Sy2 -type cyclization. This reaction proceeded with a high degree of diastereoselectivity. An excellent review of this type of cyclization reaction is now available elsewhere40. 

The method of Fan and Dasgupta (1994) relics on tlie reaction of formaldehyde with 1,3-cyclohexane-dione in acidified ammonium acetate to form the fluorescent dihydropyridine derivative in a flow injection analysis system. Formaldehyde trapped in water can be reacted with pararosaniline and sodium sulfite under mild conditions (neutral pH, room temperature equilibration) to produce a colored product that is measured at 570 nm (Petreas et al. 1986). The presence of bisulfite is an interference in this reaction so the method cannot be used to sample atmospheres that contain sulfur dioxide. In addition, the method is reported to suffer from interferences resulting from the presence of other aldehydes and phenol (Hoogenboom et al. 1987). The indirect method of Hoogenboom et al. (1987) relies on the reaction of excess bisulfite in an aqueous solution of formaldehyde with 5,5 -dithiobis(2-nitrobenzoic acid) to form a colored product, the absorbance of which is measured at 412 nm. The method reported by Naruse et al. (1995) relies on the formation of a colored product obtained by reacting the aqueous formaldehyde with acetylacetone and ammonium acetate in acetic acid. Absorbance is measured at 414 nm. 

Periodate can be determined by its redox reaction with o-dianisidine [35], benzhydrazide [36], or 2,2 -azinodi(3-ethylbenzothiazolesulphonic acid) [37] and phthalimide-bisthiosemicarbazone (e = 2.8-10 ) [38]. Cyclohexane-1,3-dione bis-thiosemicarbazone [39], 3,4-dihydroxybenzaldehyde guanylhydrazone [40], salicylaldehyde guanylhydrazone [41], and amyloride hydrochloride [42] allow IO4 to be determined in the presence of 103". 

Farage and Janjic (1982-1 and 2) observed oscillations in the concentrations of bromide and redox potentials during the uncatalyzed oxidation of 1,4-cyclohexane-dione by bromate in sulfuric, nitric (1982-1), perchloric and orthophosphoric (1982-2) acid solutions. The system does not require a catalyst such as the redox couple Ce(IV)/Ce(III) or Mn(III)/Mn(II) of the B-Z reaction. Experimenting with this system Farage and Janjic (1982-3) observed that temperature, stirring and oxygen affect the frequency or amplitude of oscillations. 

An attempt to prepare reduced S-quinolinones from cyclohexane-1,3-diones (or their tautomers) and 3-amino-2-metbyiacrolein gave 1,8-acridinediones with the loss of one carbon atom (a mechanism for this reaction has been suggested). The acridinediones were also synthesized (in 40-79% yield) from the cyclohexane-diones, propanal and ammonium acetate. Further investigation of the former synthesis showed that quinolinones are also produced in the reaction but as they are oils, they had to be isolated as their salts (see also Chapter 53). 

Formaldehyde Foods Microwave for accelerating Fluorimetry 0.02 ng ml, 1 the Hantzsch reaction with cyclohexane 1,3-dione Flow injection system sample stopping [429] inside the microwave oven ... 

Treatment of the monoketal of cyclohexan-l,2-dione 36 with 2-pyridyllithium, a reaction used previously in conjunction with the synthesis of a degradation product (Scheme 5), gave in 66% yield the alcohol 37 which upon hydrogenation followed by hydrolysis and acetylation yielded the two diasteriomeric a-ketols 184 and 185... 

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