Reaction of 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine with pregnenolone derivatives

New androsteno[17,16-d]pyrazoles and -pyrazolines with pyrazolo[3,4-d]pyrimidine fragments were synthesized. A reaction of 3β-hydroxypregna-5,16-dien-20-one and its 3-O-acetyl derivative with 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine led to hydrazones at position 20 of the pregnenolone molecule, a possibility of their cyclization was studied. Upon melting, the hydrazones cyclize with the formation of pyrazoline ring annulated with ring D of the steroid at positions 16 and 17. Reflux of the hydrazones in mesitylene with AcOH leads to a mixture of two reaction products: androsteno[17,16-d]pyrazole and a dodecahydro-13H-phenanthro[1′,2′:5,6]pyrano[2,3-d]pyrazole derivative. Apparently, this transformation proceeds through the corresponding epoxide with subsequent rearrangement, which leads to the ring D expansion.     

1,3-Dipolar cycle-addition of 2-diazoalkanes to pyridazin-3(2H)-one derivatives. The formation of 3H-pyrazolo[3,4-d]pyridazin-4(5H)-one and 3H-pyrazolo[3,4-d]pyridazin-7(6H)-one derivatives

1,3-Dipolar cycloadditions of diazoalkanes to pyridazin-3(2H)-ones 1–7 and pyridazin-3(2H)-thiones 8 and 9 are regioselective producing 3H -pyrazolo[3,4-d]pyridazin-4(5H)-ones 15–19, 27–29 and 34–38 as the major products. In some instances, the isomeric 3H-pyrazolo[3,4-d]pyridazin-7(6H)-ones, such as 20 and 23 were isolated as the minor products. From 3 and 6 the primary 3a,7a-dihydro cycloadducts 25 and 26 , and rearranged 1,2-dihydro intermediate 31 were isolated. From 10 and 1-diazoindane the isomeric exo- and endospiro products 39 and 40 were formed.     

Synthesis of Novel [1,2,4]Triazolo[3,4-d][1,5] Benzodiazepinones Derivatives by 1,3-Dipolar Cycloaddition

Cycloaddition of N-aryl-C-ethoxycarbonylnitrilimines and diarylnitrilimines on 1,5-benzodiazepinones was achieved in a one-pot procedure, to give a variety of compounds possessing an additional heterocyclic ring fused to the heterocyclic nucleus. This reaction was revealed to be completely peri and regioselective. The structures were elucidated by spectral methods and X-ray crystallographic analysis.     

Stereoselective [3,3]-sigmatropic rearrangement promoted by the metal [1,3]-shift of binuclear Fischer carbene complexes

Reaction of chiral homobinuclear Fischer chromium carbene complexes with allyl alcohol in the presence of NaH and the following oxidative demetalation gave alpha-allyl esters in up to 97% ee via [3,3]-sigmatropic rearrangement reaction promoted by the metal 1,3-shift. On the other hand, chiral heterobinuclear tungsten carbene complexes with arene chromium complexes afforded alpha-allyl-beta-hydroxy esters as a major product in up to 92/8 dr by the same reaction sequence.     

Solvent-free combinatorial synthesis of tetrazolo[1,5-a]thiopyrano[3,4-d]pyrimidine derivatives

A series of novel tetrazolo[1,5-a]thiopyrano[3,4-d]pyrimidine derivatives were synthesized by reaction of aryl aldehyde, 2H-thiopyran-3,5(4H,6H)-dione, and 5-aminotetrazole under solvent-free conditions. The features of this procedure are mild reaction conditions, high yields, and operational simplicity.     

Pyridazines. XLI synthesis of novel pyrido[3,4-d]pyridazine derivatives from 4,5-disubstituted pyridazines

Pyrido[3,4-d]pyridazines 2–5, 21 bearing one, two, or three aryl substituents in the pyridine moiety are shown to be conveniently accessible from 4-aroyl-5-methylpyridazines or 4,5-diaroylpyridazines, respectively, by condensation reactions with appropriate C-N fragments. In addition, the novel pyridazine-annelated pyridones 24, 25 were found to be easily available from ethyl 5-methyl-4-pyridazinecarboxylate.     

The synthesis and transformations of 9H-imidazo[1,2-b]pyrazolo[4,3-d]-pyridazine and 9H-pyrazolo[4,3-d]-s-triazolo[4,3-b]pyridazine derivatives

The nucleophilic and electrophilic substitutions of 6-substituted 9,9-dimethyl-9H-imidazo[1,2-b]pyrazolo- [4,3-d]pyridazines 2 , nucleophilic substitutions of 6-substituted 9,9-dimethyl-9H-pyrazolo[4,3-d]-s-triazolo- [4,3-b]pyridazines 7 and some other transformations to give compounds 3 and 8 , respectively, were studied. It was shown that both heterocyclic systems are stable under the conditions employed in these transformations.     

Synthesis of 4-substituted 1,5-diaryl-3-diphenylmethoxy-3-pyrrolin-2-ones and their [1,5]-sigmatropic rearrangement

Reactions of 1,4,5-trisubstituted 3-hydroxy-3-pyrrolin-2-ones with diphenyldiazomethane yield the O-alkylation products. Thermolysis of 1,5-diaryl-4-heteroyl-3-hydroxy-3-pyrrolin-2-ones is accompanied with suprafacial [1,5]-sigmatropic rearrangement.     

Protonation of 4-hydroxypyrazolo[3,4-d]pyrimidine and its methyl derivatives

The ability of 4-hydroxypyrazolo[3,4-d]pyrimidine and its methyl derivatives to form mono- and dications was shown by UV and PMR spectroscopy; an assumption regarding the structures is expressed on the basis of the data obtained.     

The zwitterion-accelerated [3,3]-sigmatropic rearrangement of allyl vinyl sulfoxided to sulfines. A specific class of charge-accelerated rearrangement

Conversion of allyl vinyl gulf oxides 5 and 8 to γ, δ-unsaturated sul fines 6 and 9, respectively, under neutral conditions shows that the accelerating effects of the charges in a zwitterionic moiety do not cancel, instead the sulfoxide functionality significantly facilitates the rearrangement.     

Aminomethylation of 4-hydroxypyrazolo[3,4-d]-pyrimidine and its methyl derivatives

The Mannich reaction was used to synthesize a series of mono- and bisaminomethyl derivatives of 4-hydroxypyrazolo[3,4-d]pyrimidine and its methyl analogs, the structures of which were studied by PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1414–1417, October, 1973.     

Five-membered 2,3-dioxoheterocycles 15. Synthesis and [1,3]-sigmatropic rearrangement of 1,5-diaryl-3-diphenylmethoxy-4-ethoxycarbonyl-2,5-dihydropyrrol-2-ones

Ethyl oxaloacetate reacts with a mixture of an aromatic aldehyde and an arylamine to give 1,5-diaryl-4-ethoxycarbonyltetrahydropyrrole-2,3-diones, which react with diphenyldiazomethane to give the O-alkylation products. On heating, the latter undergo suprafacial [1,3]-sigmatropic rearrangement to 1,5-diaryl-4-diphenylmethyl-4-ethoxycarbonyltetrahydropyrrole-2,3-diones. The effects of the type of migrating group on the rearrangement are discussed.For Communication 14, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 753–757, June, 1990.     

Thermal rearrangement of 3H-pyrroles by competitive [1,5]-sigmatropic shifts,and the reversibility of the 3H- to 2H-pyrrole interconversion

3-Ethoxycarbonyl-3H-pyrroles are converted via thermal (l,5]-ester shifts to the isomeric lH-pyrrole-4- and N-esters. Isolable intermediate 2H-pyrroles are converted into the same products, and also into the 3H-pyrroles, demonstrating conclusively the reversibility of the 3H- to 2H-pyrrole interconversion.     

Asymmetric version of P-S to P-C [1,3]-sigmatropic rearrangement in the ferrocene series

The synthesis of new 2-sulfanylferrocenylphosphonates and derivatives has been achieved through a P-S to P-C [1,3]-sigmatropic rearrangement. The asymmetric version of this reaction has been successfully performed starting from a ferrocenylphosphorodiamidothioate and afforded, as a single diastereoisomer, enantiomerically pure planar chiral ortho-thio-substituted ferrocenyl phosphorodiamidate.     

A new approach to the synthesis of trifluoromethylated products of the [3,3]-sigmatropic rearrangement

CH-acids of general formula CF₃CH(X)CF₃ (X = CF₃, CO₂R) react with 2,3-unsaturated alcohols in the presence of bases to give trifluoromethylated products of the [3,3]-sigmatropic rearrangement. These reactions provide a convenient method for the synthesis of 2-alkenyl-2-trifluoromethylmalonates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1273–1277, July, 1994.