Synthesis of 4,5-dihydroisoxazoles from <Emphasis Type="Italic">N</Emphasis>-nitroso-4,5-dihydropyrazoles

N-Nitroso-4,5-dihydropyrazoles obtained from ethyl(methyl) 5-aryl-4,6-dioxo-1,3a, 4,5,6,6a-hexahydropyrrolo[3,4-c]pyrazole-3-carboxylates and ethyl(methyl) 7-aryl-6,8-dioxo-1,2,7- triazaspiro[4.4]non-2-ene-3-carboxylates eliminate nitrogen molecule on heating to afford the corresponding 4,5-dihydroisoxazole derivatives.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1561–1565.Original Russian Text Copyright © 2004 by Molchanov, Stepakov, Kostikov.     

Über ein 4,5;7,9-Bis-epoxy-hasubanan

Reaction of the enol ether1 with N-bromoacetamide in methanol gave the 7 -bromoacetal3 which rearranged in acidic media to the 7,9-epoxide5. As an oxide bridge from C-9 to C-7 in indolinocodeinone can only be formed in the -position, the isolation of5 is the chemical proof of the configuration at C-9.     

Halogen bonding in 1,2‐dibromo‐4,5‐dimethoxybenzene and 1,2‐diiodo‐4,5‐dimethoxybenzene

An interesting case of `halogen‐bonding‐promoted' crystal structure architecture is presented. The two title compounds, C₈H₈Br₂O₂ and C₈H₈I₂O₂, have almost indistinguishable molecular structures but very different spatial organization, and this is mainly due to differences in the halogen‐bonding interactions in which the different species present, i.e. Br and I, take part. The dibromo structure exhibits a π‐bonded columnar array involving all four independent molecules in the asymmetric unit, with intercolumnar interactions governed by C—Br...Br—C links and with no C—Br...O/N interactions present. In the diiodo structure, instead, the C—I...O synthon prevails, defining linear chains, in turn interlinked by C—I...I—C interactions.     

4,5‐Diazafluoren‐9‐ol

The title compound, C₁₁H₈N₂O, has two crystallographically independent mol­ecules in the crystal. Each mol­ecule is basically planar except for the O atom. The two N atoms in the mol­ecule show different behaviour as hydrogen‐bonding acceptors. One of them is involved in intermolecular O—H?N hydrogen bonds which stabilize the crystal packing.     

Synthesis of 4,5-decamethyleneimidazole, 4,5-decamethyleneoxazole, 4,5-decamethyleneisoxazole, 4,5-decamethyleneimidazolone-2, and 4,5-decamethylenepyrazole from cyclododecanone derivatives

4,5-Decamethyleneimidazole, 4,5-decamethyleneoxazole, and 4,5-decamethyleneimidazolone-2 were synthesized by reactions of 2-bromocyclododecanone and 2-hydroxycyclododecanone with formamide, ammonium formate, and urea, respectively. Condensation of 2-formylcyclododecanone with hydroxylamine and hydrazine hydrate resulted in 4,5-decamethyleneisoxazole, and 4,5-decamethylenepyrazole, respectively.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 891–893, May, 1994.     

Reactivity of the 4,5‐Didehydroisoquinolinium Cation

The chemical properties of a 1,8‐didehydronaphthalene derivative, the 4,5‐didehydroisoquinolinium cation, were examined in the gas phase in a dual‐cell Fourier‐transform ion cyclotron resonance (FT‐ICR) mass spectrometer. This is an interesting biradical because it has two radical sites in close proximity, yet their coupling is very weak. In fact, the biradical is calculated to have approximately degenerate singlet and triplet states. This biradical was found to exclusively undergo radical reactions, as opposed to other related biradicals with nearby radical sites. The first bond formation occurs at the radical site in the 4‐position, followed by that in the 5‐position. The proximity of the radical sites leads to reactions that have not been observed for related mono‐ or biradicals. Interestingly, some ortho‐benzynes have been found to yield similar products. Since ortho‐benzynes do not react via radical mechanisms, these products must be especially favorable thermodynamically.     

3-Chlor-4,5-dihydrofuran - ein nützlicher Synthesebaustein

3-Chloro-4,5-dihydrofuran can be easily substituted in the 2-position by metalation with butyllithium followed by treatment with an electrophilic reagent. The resulting derivatives may be dehalogenated to give compounds where the original ring structure is either retained or opened. In the latter case alk-3-yne-1-ols, and 1-hydroxy-4-alkanones are formed.     

4,5‐Di­azafluoren‐9‐one benzoyl­hydrazone monohydrate

The title compound, C₁₈H₁₂N₄O·H₂O, adopts the keto tautomeric form and the azomethine C=N double bond is in the E configuration. The dihedral angle between the planes of the di­aza­fluorene moiety and the phenyl ring is 11.3 (1)°. In the solid state, the mol­ecules form infinite chain‐like structures via O—H?N hydrogen bonds involving the water mol­ecules and di­aza­fluorene moieties.     

Molecular structure of 6,6-dimethyl-2-dimethylamino-2-oxo-4,5; 7,8-dibenzo-1,3,6,2-dioxasilaphosphocin and 2-methyl-2,6-dioxo-4,5; 7,8-dibenzo-1,3,2-dioxaphosphocin

An x-ray structural investigation of the synthesized title compounds (1) and (2) has been performed. The heterocycle of 1 has a boat-chair conformation with the P²=O² bond in the axial position. The heterocycle of 2 has a distorted-boat conformation with the C⁶=O carbonyl in the plane of one of the fused benzene rings. The P²=O² bond is in a pseudoequatorial position.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan' Scientific Center, Russian Academy of Sciences, 420083 Kazan'. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 2, pp. 329–334, February, 1992.     

Formation of 6,10‐Diphenyl‐Substituted Heptalene‐4,5‐dicarboxylates

It is shown that 4,8‐diphenylazulene ( 1 ) can be easily prepared from azulene by two consecutive phenylation reactions with PhLi, followed by dehydrogenation with chloranil. Similarly, a Me group can subsequently be introduced with MeLi at C(6) of 1 (Scheme 2). This methylation led not only to the expected main product, azulene 2 , but also to small amounts of product 3 , the structure of which has been determined by X‐ray crystal‐structure analysis (cf. Fig. 1). As expected, the latter product reacts with chloranil at 40° in Et₂O to give 2 in quantitative yields. Vilsmeier formylation of 1 and 2 led to the formation of the corresponding azulene‐1‐carbaldehydes 4 and 5 . Reduction of 4 and 5 with NaBH₄/BF₃ ? OEt₂ in diglyme/Et₂O 1 : 1 and BF₃ ? OEt₂, gave the 1‐methylazulenes 6 and 7 , respectively. In the same way was azulene 9 available from 6 via Vilsmeier formylation, followed by reduction of azulene‐1‐carbaldehyde 8 (Scheme 3). The thermal reactions of azulenes 1, 6 , and 7 with excess dimethyl acetylenedicarboxylate (ADM) in MeCN at 100° during 72 h afforded the corresponding heptalene‐4,5‐dicarboxylates 11, 12 , and 13 , respectively (Scheme 4). On the other hand, the highly substituted azulene 9 gave hardly any heptalene‐4,5‐dicarboxylate.     

Synthesis of 2-amino-4,5-disubstituted 3,5-dicyano-4,5-dihydrofurans

A new reaction was found for the preparation of difficult-to-obtain polyfunctional dihydrofurans, viz., the reaction of tetracyanoethylated ketones with hydrogen peroxide in the presence of a base.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1027–1030, August, 1985.