Reactions of alkyl diazoacetates with pyridinium ylides

Tomilov, Yu. V.; Platonov, Dmitry N.; Dorokhov, D. V.; Нефедов, О. М.

doi:10.1007/s11172-005-0349-6

Cited by 6 publications

(3 citation statements)

References 3 publications

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“…Methyl 6 (4 fluorobenzoyl)methyl 5 (4 fluorophenyl)pyridazine 3 carboxylate (6d) was identified by the 1 H and 13 C NMR spectra by subtracting the signals of the de scribed above pyridazine 5d. 1 Reaction of methyl diazoacetate with 4 bromophenacyl pyridinium bromide in an aqueous solution. Similarly to the previ ous experiment, the reaction of 4 bromophenacylpyridinium bro mide (1.07 g, 3 mmol) and methyl diazoacetate (0.10 g, 1 mmol) in an H 2 O-MeCN mixture (14 mL, 9 : 1) afforded 0.61 g of a mixture of pyridazines 5e and 6e, which were analyzed using the 1 Н and 13 С NMR spectra (the total yield and the ratio of pyridazines 5e and 6e are listed in Table 3).…”

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Cascade reactions of diazocarbonyl compounds with pyridinium aroylmethylides accompanied by water or benzoic acid elimination in the cyclocondensation step

et al. 2011

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The reaction of pyridinium aroylmethylides with diazocarbonyl compounds proceeds as a multistep process involving three ylide molecules and one diazo compound molecule. As a result, intermediate functionally substituted azines, if they contain carbonyl groups and reac tive methylene fragment, undergo intramolecular cyclocondensation to form tri and tetrasub stituted pyridazines. Depending on stereochemistry of cyclic ketols formed, water or benzoic acid is eliminated to form tetra or trisubstituted pyridazines, respectively. The regularities of reactions of pyridinium ylides with diazo compounds are discussed depending on the nature of substituents in the both substrates and reaction conditions.

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confidence: 99%

Cascade reactions of diazocarbonyl compounds with pyridinium aroylmethylides accompanied by water or benzoic acid elimination in the cyclocondensation step

et al. 2011

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“…Under more drastic conditions (boiling xylene in the pres ence of pyridine), tetramethyl pyrroletetracarboxylate (2) has been isolated as the major reaction product. Presum ably, these heterocyclic compounds can form via genera tion of intermediate pyridinium ylides followed by their reactions with a diazo compound.…”

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“…2 The reaction rate and pathway depend on both the polarity of the medium and the temperature. This allowed us to isolate two novel acyclic intermediates 4 and 5 that are precursors of compounds 1 and 2.…”

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Cascade reactions of nitrogen-and phosphorus-containing ylides with methyl diazoacetate and in situ generated diazocyclopropane

et al. 2006

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Reactions of pyridinium or phosphorus ylides with diazo esters are multistep processes. The first step is covalent bonding between the ylide C atom and the terminal N atom. This is followed by elimination of the ylide forming molecule and successive addition of one or two ylide fragments. Depending on the nature of the starting reagents, this type of transformations leads to novel polyfunctional phosphorus ylides or, with pyridinium ylides, to polyalkyl 3,4(4,5) diazaalkadienetri or tetracarboxylates. A reaction of the in situ generated diazocyclopropane with methyl triphenylphosphoranylideneacetate stops at the first step, giving a cyclopropylazo containing ylide. Reactions of the latter with acyl chlorides yield six membered heterocyclic betaines with a triphenylphosphonium substituent.Earlier, 1 we have found that carbene decomposition of methyl diazoacetate in boiling pyridine unexpectedly yields tetramethyl tetrahydropyridazine 3,4,5,6 tetra carboxylate (1) as a mixture of two geometrical isomers. Under more drastic conditions (boiling xylene in the pres ence of pyridine), tetramethyl pyrroletetracarboxylate (2) has been isolated as the major reaction product. Presum ably, these heterocyclic compounds can form via genera tion of intermediate pyridinium ylides followed by their reactions with a diazo compound. 1 To verify this assump tion, we have studied 2 reactions of alkyl diazoacetates with pyridinium ylides generated from other precursors (e.g., quaternary pyridinium salts prepared from haloacetic acid esters proved to be convenient precursors of such ylides 3 ).In fact, reactions of alkyl diazoacetates with pyridinium methoxycarbonylmethylide (3a) generated by decompo sition of a pyridinium salt with K 2 CO 3 ultimately af forded the same heterocycles 1 or 2 in 40-70% yields (Scheme 1). 2 The reaction rate and pathway depend on both the polarity of the medium and the temperature. This allowed us to isolate two novel acyclic intermediates 4 and 5 that are precursors of compounds 1 and 2. Rear rangement of azine 4 into diazadiene 5 followed by cy clization of the latter into tetrahydropyridazine 1 are ac celerated by bases or polar solvents.Using the starting compounds with different ester groups, e.g., (methoxycarbonyl)methylpyridinium iodide and ethyl diazoacetate, we found, from the numbers of the COOMe and COOEt groups in reaction products, that the formation of diazadienes 4 and 5 involves three ylide molecules and only one diazo ester molecule. 2 These results motivated us to study in more detail reactions of diazo compounds with ylides. Results and DiscussionPreviously, 2 we have determined only the final steps of multistep reactions of diazoacetate with ylides that first give rise to open structures 4 and 5 and then to hetero cyclic tetraesters 1 or 2. Here we tried to elucidate the character of cascade transformations during reactions of diazo compounds with ylides. In the hope of isolating products characteristic of the earlier steps of this process, we varied the nature (and, accordingly, react...

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