F Diketene

Chromium(II) chloride, 4052 Cyclohexanone oxime, 2452 l,4-Dicyano-2-butene, 2311 Diethyl dicarbonate, 2444 Diethyl sulfate, Iron, Water, 1710 (Difluoroamino)difluoroacetonitrile, Hydrazine, 0630 Difluoroammonium hexafluoroarsenate, 0098 1,1-Difluorourea, 0398 Dihydroxymaleic acid, 1447 f Diketene, Acids, or Bases, or Sodium acetate, 1441 /V. /V-Dimcthylacctamidc. 1656... 

Ammonium dichromate, 4246 Azoformamide, 0816 Azoisobutyronitrile, 3011 Azoisobutyronitrile, 3011 f tert-Butyl peroxybenzoate, 3401 4-Chloronitrobenzene, 2142 f 1,1-Difluoroethylene, 0700 f Diketene, 1441... 

Diallyl sulfate, 2437 f 1,1-Dichloroethylene, 0691 l,4-Dicyano-2-butene, 2304 Diisocyanatomethane, Dimethylformamide, 1076 f Diketene, Acids, or Bases, or Sodium acetate, 1437... 

Ammonium dichromate, 4240 Azoformamide, 0812 Azoisobutyronitrile, 3006 Azoisobutyronitrile, 3006 f ferf-Butyl peroxybenzoate, 3397 4-Chloronitrobenzene, 2135 f 1,1-Difluoroethylene, 0696 f Diketene, 1437... 

Miller, F. A., and S. D. Koch Diketene Infrared Spectrum and Structure. 

Kato et al,94 reported that 2-amino-6-methylpyridine and diketene did not yield 4-oxo-4/f-pyrido[l,2-a]pyrimidines but instead yielded 2-acetyl-acetamido-6-methylpyridine and pyridone or pyrone derivatives. 2-Methyl-4-oxo-4H-pyrido[l,2-a]pyrimidine (47) and its 8-methyl derivative have also been prepared from 2-aminopyridine and 2-amino-4-methylpyridine with N,N-dimethyl-3-aminocrotonamide95 or with acetoacetamide45 in yields of 5 and 39°,. respectively. 

Methylenemagnesium, 0401 f 4-Methylene-2-oxetanone, see Diketene, 1437 f Methyl ethanoate, see Methyl acetate, 1228... 

A relatively large number of papers has described the preparation of oxo derivatives of 3,4-dihydro-2/f-1,3-oxazine. The previously reported1 use of diketene as a cyclizing agent has found wider application. Gunar et a/.178 described the reaction of diketene with ammonium thiocyanate. It passes through an intermediate acetoacetyl isothiocyanate to a 2-thiono derivative, which, on oxidation, yields 50 [Eq. (37)]. 

Fig. 6.25. Acylation of alcohols with a diketene (A preparation Section 15.4). The reaction product is the acetoacetic ester F.

Trisubstituted six-member carbocycles were also prepared. Condensation of LI with commercial acetoacetanUides 9.14a-f produced, by one-pot Michael addition and Robinson annulation, the cyclohexenone library L4 (7680 members. Fig. 9.11). Noncommercial acetoacetamides Mi, prepared by condensation of diketene 9.15 with 40 primary and secondary amines (structures not shown in the paper), were used as monomers and condensed with a 320-member LI subset to give the expanded cyclohexenone library L5 (12,800 members). Difficulties in preparing extremely large discrete libraries, even using fuUy automated robotic workstations, and the need to diversify the screening set obliged the authors to limit the number of monomers and chalcones for any specific library/scaffold (see also LIO below). 

Prepared by reaction of diketene with f-butanol in the presence of sodium eth-oxide, the reagent is employed in a novel synthesis of acyloins. The reagent (1) is alkylated as enolate, the product (2) is converted into its enolate (3), and the... 

Two short formal total syntheses were reported by Fujisawa, both employing diketene derivatives for C-1 to C-4 of the carbon framework. In the first sequence, Grignard reagent 38 was treated with 3-lactone 39 and a catalytic amount of Cul to afford allene 40 after acidic workup (Scheme 2.5). Base isomerization to a mixture of (f.Fj-and ( ,Z)-diene isomers 41 occurred in 85% overall yield. Lactonization using the Yamaguchi procedure (trichlorobenzoyl... 

Stockelmann et al. reacted 2-amino-3-methylpyridine and 2-amino-4-methylpyridine with diketene in water. The 2-oxo-2//-pyrido[l,2-a]pyri-midine structure was assigned to the products, reportedly obtained in 90 and 97" yields. Kato et al. and Yale et subsequently demonstrated that the products were 4-oxo-4/f-pyrido[l,2-a]pyrimidines and the yields were not higher than 16" . 

Several strategies for the synthesis of polymer-bound enones have been described. One way is to start from immobilized [f-ketoesters, which can be prepared via transesterfica-tion of Wang resin with alkyl fl-keto carboxylates [31], or by treatment with diketene [16]. Knoevenagel reactions of these polymer-bound [f-ketoesters with aldehydes led to the formation of 2-alkylidene- or arylidene-P-ketoesters (Fig. 6.19 (A)). 

J. Heller, D.W.H. Penhale and R.F. Helwing, Preparation of poly(ortho esters) by the reaction of diketene acetals and polyols, J. Polym. Sci., Polym. Letter Ed. 1980, 18, 619-624. 

BROMOETHANE (74-96-4) Forms explosive mixture with air (flash point -4°F/ —20°C). Hydrolyzes in water, forming hydrogen bromide. Contact with oxidizers, diethyla-luminum hydride, chemically active metals aluminum, magnesium, or zinc powders, lithium, potassium, sodium. May cause fire or explosions. Incompatible with alcohols, diketene. Attacks some plastic, rubber, and coatings. 

DIKETENE (674-82-8) Forms explosive mixture with air (flash point 91°F/33°C). Violent reaction with water, oxidizers. Violent polymerization or explosion caused by elevated temperatures, acids, amines, bases, or sodium acetate. Incompatible with alcohols, halons. A storage hazard can decompose, causing explosion add inhibitor. 

ETHENONE (463-51-4) Slowly hydrolyzes in water, releasing ammonia and forming acetate salts. This process is accelerated with heat in an acid or caustic environment. Reacts vigorously with water and a wide variety of organic compounds. Forms explosive compound when mixed with hydrogen peroxide. Can dimerize to diketene even at low temperatures diketene forms an explosive mixture with air (flash point 90°F/32°C). Reacts with ammonia, forming acetamide. Reacts violently with oxidizers, forming unstable and explosive diacetyl peroxides violent polymerization is possible. 

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