IR spectra and crystal structure of hydrochlorides and complex salts of 2,3-polymethylene-3,4-dihydroquinazolines and-4-quinazolones

IR spectra are reconsidered on the basis of the results of x-ray structural analysis of the crystal structures of hydrochlorides and complex salts of 2,3-polymethylene-3,4-dihydroquinazolines and-4-quinazolones. It has been established that two absorption bands (Nl⁺–H) in the complex salts characterize different energies of formation of an H-bond, which is weaker than in the corresponding hydrochlorides. The nature of an absorption band in the 3400–3500 cm^–1 region has been established from the XSA results.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (371) 120 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 364–367, May–June, 1999.     

Mass spectra of 2,3-polymethylene-3,4-dihydroquinazolin-4-ones with substituents at C9

Summary The main fragments in the mass spectra of the 2,3-polymethylene-3,4-dihydroquinazolin-4-one with six- and seven-membered alicyclic rings are formed by the decomposition of ring C through the stage of the cleavage of the C₉-C₁₀ bond, while the compound with a five-membered ring ejects a hydrogen atom.A hydroxy group at C₉ initiates the appearance of fragments due to the initial cleavage of the C₂-C₉ bond. In the spectra of the halogen and acetoxy derivatives the fragmentation of the alicyclic ring is suppressed and the main fragmentation pathway is the splitting out of the substituent. The hypothesis of the protonation of the N₁ nitrogen atom has been adopted to explain the stability of a number of the ions.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 180–187, March–April, 1979.     

Quinazolines. 13. Some reactions of 2,3-polymethylene-3,4-dihydro-4-quinazolones with electrophilic reagents

2,3-Polymethylene-3,4-dihydro-4-quinazolones react with bromine and sulfur trioxide to give complexes involving the nitrogen atom, while bromination in acidic media and Vilsmeier-Haack formylation lead to replacement of the hydrogen atoms of the carbon atom in the position. Their nitration and chlorosulfonation give 6-nitro- and 6-chlorosulfonyl-2,3-polymethylene-3,4-dihydro-4-quinazolones. Some of the chemical transformations of the synthesized compounds were studied.See [1] for Communication 12.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 684–691, May, 1979.     

Spectral and structural correlations of 1,4- and 3,4-dihydroquinazolines

Alkylation of the nucleophilic addition product of 2,4-diphenylquinazoline and organometallic derivatives produced a mixture of 1,4- and 3,4-dihydroquinazoline dreivatives. The structures were established through pmr correlations of chemical shifts of the N-CH₃ groups produced when the alkylating agent was methyl iodide. Spectra (uv, pmr) of known open-chain amidines were used to confirm the structures of the isomeric dimethyl 2,4-diphenyldihydroquinazolines. The uv spectra of 2-phenyl-3,4-dihydroquinazolines possessed an absorption maximum at 320 nm while the 1,4-dihydroanalogues had a maximum at 290 nm. Characteristic absorptions in the 1550–1650 cm^?1 region of the infrared spectra also differentiated these two groups of compounds. Removal of the 2-phenyl substituent renders these correlations less reliable.     

Nitrogen bridgehead compounds. Part 35. Structures of α-formyl-2,3-polymethylene-3,4-dihydroquinazolin-4-ones

The structures of the title compounds bearing a five-, six- or seven-membered A ring have been investigated by uv and ¹H and ¹³C nmr spectroscopy. The imine-enol-enamine (I-II-III) tautomerism of these compounds depends greatly on the ring size. A significant solvent-dependence is observed only for the five-membered-ring compounds 1 and 2 , which in ethanolic solution exist predominantly in the imine form I, and in chloroform solution in the enol form II. The compounds with a six-membered A ring, 3 and 4 , are mainly in the enamine form III. On protonation, 3 and 4 change into the E and Z isomeric mixture of the enol tautomer II. The seven-membered-ring compound 5 is a mixture of the imine I and the enamine III tautomers.     

Solid-phase synthesis of 3-alkyl-2-arylamino-3,4-dihydroquinazolines

The solid-phase synthesis of 3-alkyl-2-arylamino-3,4-dihydroquinazolines using an N-Fmoc-β-amino-2-nitrobenzenepropanoic acid scaffold is described. The resin-bound scaffold was reductively alkylated with aldehydes or ketones after Fmoc deprotection, followed by reduction of the nitro group with tin(II) chloride. Subsequent cyclization of the 1,3-diamine intermediates with aryl isothiocyanates in the presence of 1,3-diisopropylcarbodiimide (DIC) afforded the desired products in high purity with moderate to good yield after trifluoroacetic acid (TFA) cleavage.     

Low-melting molecular complexes: Part VII. 2,3-, 2,5- and 3,4-hexanediones and their molecular complexes with chloroform

Crystals of three isomeric 2,3-, 2,5- and 3,4-hexanediones 1–3 and of molecular complexes (1:2) of 2 and 3 with chloroform (4 and 5) were grown by in situ cryocrystallisation and characterised by single-crystal X-ray crystallography. The intermolecular interactions and packing motifs were examined using the analysis of pairwise energies of intermolecular interactions. The method has revealed the importance of carbonyl…carbonyl interactions in the structures 1, 3 and 4 and the relatively weaker halogen bonds in the structures 4 and 5.     

Rhodium-catalyzed direct C-H addition of 3,4-dihydroquinazolines to alkenes and their use in the total synthesis of vasicoline

The inter- and intramolecular couplings of unactivated alkenes to 3,4-dihydroquinazolines with a Rh(I) catalyst are reported. Coupling between olefins and NH-3,4-dihydroquinazoline was found to occur consecutively with heterocycle dehydrogenation in the presence of a Rh(I)/PCy3/HCl catalyst. The reaction was used to develop an effective method for the synthesis of 2-substituted quinazolines through an oxidative workup step. The regiocontrolled synthesis and Rh-catalyzed cyclization of alkene-tethered 3,4-dihydroquinazolines are also described. Applying this method, the second total synthesis of vasicoline was achieved. The key Rh-catalyzed cyclization step was made possible by the use of a rigid bicyclic phosphine ligand. The synthesis further demonstrates a challenging Cu-catalyzed amidation of an ortho-substituted aryl chloride.     

X-ray structural investigation of tricyclic 2,3-tetra and 2,3-pentamethylene-3,4-dihydroquinazol 4-ones and their derivatives

The fine structures of the alkaloid 2, 3-tetramethylene-3, 4-dihydroquinazol-4-one and its synthetic analogs 2, 3pentamethylene-3, 4-dihydro- and -1, 2, 3, 4-tetmhydroquinazol-4-ones and the complex of 2, 3 pentamethylene3, 4-dihydroquinazol-4-one with succininide in a ratio of 2:1 have been studied by the x-ray structural method. By an analysis of the lengths of the valence bonds, including those given in the literature, the degree of delocalization of the -electron system of the N1=C2 double bond and the role of the C=O bond in the overall conjugation have been evaluated.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 410–420, May–June, 1995. Original article submitted June 20, 1994.     

Reaction of 3,4-diaminofurazan with carbonyl compounds and their metal complexes

It is shown that when 3,4-diaminofuranzan reacts with formic acid under various conditions there is, along with the mono- and diformylation, an intermolecular reaction leading to a polymeric compound. The diamine under consideration forms a monoazomethine with salicylaldehyde but a bis (azomethine) complex with the salicylaldehydate of divalent nickel.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 666–669, May, 1986.     

Nitropyridines: VI. Synthesis of 2-aryl(hetaryl)- and 2,3-polymethylene-5-nitropyridines

Previously unknown 2-aryl-, 2-hetaryl-, and 2-cyclopropyl-5-nitropyridines and 2,3-polymethylene-5-nitropyridines were synthesized by reactions of 1-methyl-3,5-dinitropyridin-2(1H)-one with various cyclic and acyclic ketones in the presence of ammonia.     

Some phosphinite complexes of Rh and Ir, their intramolecular reactivity and DFT calculations about their application in biphenyl metathesis

Biphen(OPR₂) (with R: Ph, iPr, Cy) is reacted with [Rh(COE)₂Cl]₂. The corresponding μ-chloro-bridged dimers are received. An X-ray analysis of [Biphen(OPCy₂)RhCl]₂ is included. This compound shows a dynamic behaviour in solution, ascribed to a monomer/dimer equilibrium. The difference of the Biphen ligands to Milsteins PCP pincer-type ligand is shown. A catalytic cycle for biphenyl metathesis containing the coupling of oxidative addition and reductive elimination of the bridging C-C single bond in the biphenyl fragment using Rh^I/III complexes and the concept of chelating assistance was calculated using DFT (B3PW91/LANL2DZ). According to the calculations the activation energy of the oxidative addition is about 30 kcal/mol and for the reductive elimination about 19 kcal/mol. The fac-Rh^III complex is by far the most stable compound, but the formation of it is kinetically strongly disfavoured. Pre-catalysts (COD)M(Ph-O-PR₂) (M: Rh, Ir) were synthesized by pre-coordinating the phosphinite to the metal (X-ray structures of four such compounds included) followed by treatment with 2 equiv. of sec. BuLi (X-ray structures of two such compounds included). In case of Ir this synthesis is complicated by C-H activation (X-ray structure of (COD)Ir(H)(Cl)(2-Br-phenyl-O-(diisopropylphosphinite)) included) and fast oxidative addition of the Ph-C-Halide bond. For (COD)Ir(H)(Cl)(2-phenyl-O-(diisopropylphosphinite)) the C-H activation is reversible and thermodynamic parameters for the ring closure reaction were determined by VT-NMR measurement (ΔH = −21.1 ± 0.5 kJ/mol, ΔS = −62.8 ± 1.7 J/(mol K)). The pre-catalysts were reacted with Biphen(OPR₂) to enter the calculated catalytic cycle. With Rh as center metal this reaction works out cleanly to give new complexes with the three P-atoms coordinated to one Rh center. No hemi-labile character was found for these P-donors even at 105 °C in toluene. If (COD)Rh(2-phenyl-O-(diisopropylphosphinite)) is reacted with 2 equiv. of 2-iodo-phenyl-O-(diisopropylphosphinite) oxidative addition of one C-Iodo bond is observed and the corresponding mer-Rh^III complex is received. Upon treatment with 2 equiv. of sec. BuLi the resulting product is(Biphen(OPiPr₂))Rh^I(2-phenyl-O-(diisopropylphosphinite)) rather than mer-Rh^III(2-phenyl-O-(diisopropylphosphinite))₃. Reaction of [Rh(COD)Cl]₂ with 3 equiv. of 2-bromo-phenyl-O-(diphenylphosphinite) shows a fast scrambling of the chlorine into all possible ortho positions of the phenolate rings in the final Rh^III reaction product.     

Photocycloaddition of 2,3-dimethylmaleimide to selenophene and 3,4-dimethylselenophene

Summary The benzophenone sensitized photocycloaddition of 2,3-dimethylmaleimide to selenophene and 3,4-dimethylselenophene was carried out first to generalize the photoaddition reaction of methylmaleic anhydride derivatives to selenophene, using this time the nitrogen analogue, and second to reexamine the composition of the product mixture formed in the reaction. It was found that in adition to the 1:1 adduct isolated in previous investigations, three geometrical isomers may be proposed for the 2:1 adduct (two molecules of maleimide of one of selenophene or its methyl derivative).

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Photocycloaddition von 2,3-Dimethylmaleimid an Selenophen und 3,4,-Dimethylselenophen

Zusammenfassung Die benzophenonsensitivierte Photocycloaddition von 2,3-Dimethylmaleimid an Selenophen und 3,4-Dimethylselenophen wurde durchgeführt, um erstens die Photoadditionsreaktionen von Methylmaleinsäureanhydridderivaten an Selenophen allgemein zu studieren und um zweitens die Zusammensetzung der bei der Reaktion gebildeten Produktgemische erneut zu untersuchen. Zusätzich zu dem bei früheren Arbeiten gefundenen 1:1-Addukt werden drei geometrische Isomere für das 2:1 — Addukt (2 Moleküle Maleimid und 1 Molekül Selenophen oder 3,4-Dimethylselenophen) vorgeschlagen.