C-Acetonylation

Methyl ethyl ketone was detected in experiments above lOO C. Acetonyl acetone has not been identified in the products so far. Actually, not more than a small amount of this compound is expected to be formed, since (i) the acetyl radical is unstable at higher temperatures, and (ii) the rate of formation of acetonyl radical is slow at lower temperatures. The formation of biacetonyl was observed in the investigation of the reaction between CH3 and acetone . Brin-ton ° has succeeded in detecting biacetonyl also among the products of acetone photolysis in the temperature range 200-475°C. Most of the evidence on the formation of biacetonyl in the photolysis of acetone is, however, based on material bal-ance and hence is only of secondary importance. 

Acetonyl-a(1H)-tetrazole (C-Acetonyl-tetrazol or Acetessig—tetrazotsaure, in Ger),... 

Since allylation with allylic carbonates proceeds under mild neutral conditions, neutral allylation has a wide application to alkylation of labile compounds which are sensitive to acids or bases. As a typical example, successful C-allylation of the rather sensitive molecule of ascorbic acid (225) to give 226 is possible only with allyl carbonate[l 37]. Similarly, Meldrum s acid is allylated smoothly[138]. Pd-catalyzed reaction of carbon nucleophiles with isopropyl 2-methylene-3,5-dioxahexylcarbomite (227)[I39] followed by hydrolysis is a good method for acetonylation of carbon nucleophiles. 

For example, the action of a-thiocyanatoacetone on ammonia in ether solution gives 4-methyl-2-aminothiazole but in very low yield (137). Methylamine in ether at 0°C gives in a first step S-acetonyl N-methylisothiourea (196) in 80% yield (Scheme 102) (137). The cycliza-tion of this intermediate occurs either after a prolonged rest at room temperature, either by fusion or by heating with dilute hydrochloric acid to afford the 4-methyl-2-methylaminothiazole (197). 

Hydrolytic fragmentation of the C5-N6 part took place upon heating 7-methyl-5-propyl-2-thioxo-l,2,4-triazolo[l,5-c]pyrimidine (129) with hydrochloric acid. 3-Acetonyl-5-mercapto-l,2,4-triazole (130) and butanoic acid were obtained as a result of N4-C5, C5-N6, and N6-C7 bond cleavages (65JCS3369) (Scheme 50). 

A-Acetonyl-A-benzenesulfonylamino) -fluoro-2-nitrobenzene somewhat similarly gave 6-fluoro-3-methylquinoxalme (Raney Ni, H2, AcOEt, 20°C, 5 min 22% aerial aromatization ). ... 

Introduction of an alkyl group to the C-13 position of protoberberine was simply accomplished by the reaction of dihydroprotoberberines (230-232) or their 8-acetonyl derivatives (233,234) with alkyl halides, though yields are not always satisfactory. In some cases, oxidized products, protoberberines, and/or Af-alkyl quaternary bases were concomitantly produced. 

Manganese(lll) acetate oxidation of (+)-p-menth-l-ene yields the two lactones (165 X=0, Y = CH2) and (165 X = CH2, Y = O) as major products together with anticipated acetates similar oxidation of (+)-pulegone yields the C-2 acetates in low yield and oxidation of isomenthone in the presence of isopropenyl acetate results in acetonylation at C-2 and C-4. Further examples of the rearrangement of epoxides with KOBu -aprotic solvents (pyridine is favoured) have been reported (c/. Vol. 6, p. 44), e.g. (166) to (167), although with the corresponding 1,2-epoxy-... 

Hydroxy-5-methyl-2-acetonyl 6-C-glucopyranosylchromone 2"-0-glucoside DI-C-GLYCOSYLFLAVONES Vicenin-2... 

Methoxycoumaroyl 5-methyl-7-hydroxy 2-acetonyl DI-C-GLYCOSYLFLAVONES Vicenin-1 ( ) 6"-O-Acetyl 6- C-a-L-Rhamnosylapigenin ( ) 8-C-(6" -3-Hydroxy-3-methylglutaroyl)glucoside Isoschaftoside 2" -0-Feruloyl... 

Another example is the indirect acetonylation of a 1,2,3,4-tetrahydropyridine derivative at the (3-position of the enamide system [99]. The reaction involves a double alkylation to furnish an acetylcyclopropane which undergoes fragmentation on acid treatment. It is noted that polarity alternation and ring strain relief allow the facile and regiospecific C-C bond cleavage to proceed, the intervention of a cyclopropane intermediate also leads to disjoint system. This is a fundamental strategy [100] which has been frequently employed to gain access to compounds with disjoint functionalities. 

Above 250 °C. significant amounts of methane, carbon monoxide, and methyl chloride are formed suggesting that acetonyl, acetonylidene, and chloroacetyl radicals are unstable at elevated temperatures. This contention is supported by the rise in the quantum yield of hydrogen chloride above unity at these temperatures. 

A methylene group between the oxadiazole ring and a carboxyl group acts like a malonic acid with respect to ease of loss of the carboxyl group. Likewise the acetyl group from an acetonyl side chain at C-5 is lost in basic solution, analogous to the ketone split in a fi-keto ester or / -diketone. This was recognized in the early work on oxadiazoles by Tiemann,48 Wiese,49 Richter,47 and Schubart.50... 

Comp proplnt consisting of AN 73-69, cellulose acetate ca 5 2,4-dinitrodiphenylether 3 acetonyl acetone dioxime 2-3 finely divided C 1-5%) I)E.F.Morello et al, USP 2942962 (I960) CA 54, 25830 (I960) [Addn of an aromatic amine (DPhA or dinaphthyl-amine) to proplnts of USP 2942961 renders them less susceptible to gassing at elevated temps. 

AP33 CgHioOS acetOnyl phenyl sulfide C6H5SCHsC0CH3 DMF PY Bu4NI >.15 - - 25 DME Ag/AgCt 12A0 C=1-2,EC= 1.644,1=... 

Reactions proceeding more than once in the transformation of a substrate can be more effective than a single process If the reaction in question is a condensation of an N nucleophile with a carbonyl compound, the combination of the of two such reactions—allows for the synthesis of heterocycles like, the two depicted in Figure 9.27. The synthesis of quinoxaline (B) from glyoxal dihydrate (A) and orfho-phenylene diamine consists of two imine formations. Somewhat more complicated is the synthesis of dimethylpyrrole D from acetonyl acetone (C) and ammonia. After the formation of the first imine, an imine enamine isomerization occurs. A condensation followed by another imine — enamine isomerization leads to the product. 

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