Ketene aminals 3-amino

Analogously, the reactions of ketene aminals with ketene or dimethyl ketene gave y-amino-a-pyrones and the linear acylation products, respectively 422). 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

While cycloaddition approaches have been discussed extensively in this chapter, there are certain substitution patterns that are not amendable to such approaches. In these cases, the more traditional annelative approaches are necessary. For example, the 5,6-dihydropyrrolo[3,4-rf]imidazol-4(3//)-one (286) is obtained from the diamine (285) and triethyl orthoformate. If formamide is used in excess, 6-(formamidomethylene)-5,6-dihydropyrrolo[3,4-d]imidazol-4(3//)-one (287) is obtained (Scheme 53) <70JPS1732>. A variant of the Thorpe cyclization was employed in the preparation of 3-amino-4//-pyrrolo[3,4-c]isoxazoles (289) from a-cyanooximes (288) (Equation (66)) <68JMC453>. 3-Acyltetramic acid (290 X = NR2) and 3-acyltetronic acid (292 X = O) hydrazones undergo ready cyclization in refluxing xylene with catalytic p-toluenesulfonic acid to afford 4-oxo-l,4-dihydro-6/f-pyrrolo[3,4-c]pyrazoles (291) and 4-oxo-l,4-dihydro-6//-furo[3,4-c]pyrazoles (293), respectively (Equation (67)) <82SC43l>. The novel synthesis of 5-amino-6a-hydroxydihydro-6//-pyrrolo[2,3-j]isoxazole (296) from 3,4-disubstituted 4-(amino)isoxazol-(4//)-ones (294) is hypothesized to occur by the cyclization of the ketene aminal intermediates (295) (Scheme 54) <91S127>. 

Hexahydroazocines. The synthesis of stable ketene aminal diphenylphosphates 46 was accomplished departing from the eight-membered iV-BOC or iV-COOPh protected lactams 45 via their potassium enolates (Scheme 13 <1998CC1757>). Azocane-2-one 45 was easily obtained from cycloheptanone 44 by Beckmann rearrangement of its cycloheptanone-oxime and subsequent protection of the amino moiety. 

Hydrazinoyl chlorides react with ketene aminals in the presence of triethylamine to give diaminopy-razolines (544 equation 243). From tetraaminoethylenes and amines or amine derivatives or heterocu-mulenes tris(amino)methane derivatives, e.g. (545) and (546) (Scheme 101) are formed. Reactions of this type have been reviewed. ... 

Acetic formic anhydride has been prepared by the reaction of formic acid with acetic anhydride and ketene, and of acetyl chloride with sodium formate. The present procedure is essentially that of Muramatsu. It is simpler than others previously described and gives better yields. It is easily adapted to the preparation of large quantities, usually with an increase in yield. Acetic formic anhydride is a useful intermediate for the formyl-ation of amines, amino acids, and alcohols, for the synthesis of aldehydes from Grignard reagents, and for the prejiaration of formyl fluoride. ... 

Formamidine acetate was prepared in similar high yield by a similar procedure but with glacial acetic acid as solvent.804 A A-Disubstituted formamidine and acetamidine derivatives have been obtained analogously from orthoesters and alkylamines in the presence of glacial acetic acid805 or boron trifluoride etherate 806 In the reaction of orthoesters with secondary amines in the presence of toluenesulfonic acid the formation of ketene aminals (alkyl l -amino-vinyl ethers) was also observed.807... 

Methyl-4-nitroisoxazol-5(27/)-one 10 having multifunctionalities reveals versatile reactivity to serve as a precursor for polyfunctionalized systems. Nitroisoxazolone 10 readily reacts with amines to afford a-amino-(3-nitroenamines (nitro-ketene aminals) 11 and amidoximes 12 [28] and undergoes... 

Halogenopyrimidines react with active methylene groups, such as those in diethyl malonate, ethyl cyanoacetate, ketene diethylacetal, etc. For example, 4-chloro-6-methyl-5-nitropyrimidin-2-amine (454) and dimethyl sodiomalonate give dimethyl 2-amino-6-methyl-5-nitropyrimidin-4-ylmalonate (455) (63ZOB3132) 2-chloro-4,6-... 

The condensation of activated thiols onto adjacent nitriles is a common method for the preparation of amine-substituted thiophenes. A three component condensation was utilized to prepare a-aminothiophene 11 <00TL1597>. An alternate method for preparing amino-substituted thiophenes involved the treatment of ketene S,JV-acetal 12 with an activated carbonyl compound 13 which gave thiophene 14 <00JOC3690>. This type of reaction has also been utilized to prepare building blocks for the synthesis of fused thiophenes <00JHC363>. 

Systems with one amino group and one alkylthio group as donors, commonly known as ketene /V,S-aminals, are sterically rather similar to the 1-ethyliden-amino analogs like 9 and 10 (R = Me). However, comparison of the C=C barrier in 10, where R = R = R2 = Me (14.8 kcal/mol Table 3), with that of 31 (7.4 kcal/mol Table 6) shows that the MeS group must be much more... 

The title phosphonate and related substances undergo thermal decomposition to B-acyl ketenes at temperatures in excess of 50°C. Thus thermolysis in the presence of alcohols, amines, a-hydroxy esters, and a-amino esters affords the corresponding g-keto esters and amides the latter two classes can be cyclized upon subsequent base treatment to unsaturated tetronic and tetramic acids and the related phosphonate reagents. ... 

Reaction of the amino-1,3.4-thiadiazole 86 with a series of benzaldehydes gave the arylidene amines 87 which when treated with arylacetyl chlorides and triethylamine gave 5-substituted l,3,4-thiadiazolo[3,2-fc]pyrimidin-6-ones 88 in good yields (75-95%). The reaction was thought to proceed by a (4+2) cycloaddition reaction between 87 and the ketene which was produced in situ by the interaction of arylacetyl chlorides and triethylamine <99JCR(S)36>. 

Ketene itself reacts with enamines and if in excess produces pyran-2-ones which are substituted in the 4-, 5- and 6-positions (65JOC2642). It seems likely that the acylated enamine undergoes a 1,4-addition with ketene to give an intermediate 4-amino-3,4-dihydropyranone, which eliminates the secondary amine on further reaction with ketene. 

Keywords Catalyst, Alkylation, Allylation, Arylation, Mannich reaction, Carbon-nitrogen double bond, Imine, Nitrone, Aldimine, Organozinc reagents, Silyl ketene acetal, Silyl enol ether, Amine, (3-Amino acid... 

Ketene N, O-acetals are converted to 1,1-enediamines when reacted with amines. For example, compound 45 has been prepared by substitution of the methoxy with amine (equation 16)79. Symmetric 1,1-enediamines are obtained when both the alkoxy and the amino substituents are displaced by the amine employed81. In this way, the reaction between ketene N, O-acetals 50 and piperidine leads to 1,1-dipipefidinoethylene (35) (equation 17)81. Alternatively, 35 can be prepared from the reaction of piperidine with triethyl orthoacetate82,83 or with ethoxyacetylene84, reactions which probably proceed via a ketene TV, 0-acetal intermediate. 

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