Volume 61, Issue 4

The neonicotinoids are the most successful chemical class of insecticides reaching sales of more than $1 billion in 2003, mainly due to the excellent market performance of imidacloprid and thiamethoxam. This paper describes the discovery, the synthesis and the insecticidal activity of thiamethoxam and related compounds and reports the hydrolytic stability and the degradation pathways of thiamethoxam together with the synthesis of the degradation products

This review deals with the synthesis and spectral properties of monocyclic as well as spirocyclic compounds featuring the 1,3,2-dioxaboronium or 1,3,2-dioxaborinium ring system. These compounds can be obtained by the reaction of three-valent boron compounds with enolisable 1,3- dicarbonyl compounds as well as related aza and imino derivatives

Correlations of simple and complex physical, and chemical, biological and technological properties with chemical structure are reviewed. When an adequate training set of structures and experimentally determined property values are available, the equations produced enable the prediction of these properties of molecules as yet synthesized or indeed as yet unknown. Frequently they also offer considerable insights into the manner in which the structure controls the property. Many further applications of this methodology can be anticipated

2-Aminodienes, in which the enamine function is incorporated in a five-, six-, or seven-membered ring, react with dimethyl acetylenedicarboxylate in a sequence of [2+2] cycloaddition and electrocyclic ring-opening to form the two-carbon ring expanded unsaturated heterocycles, i.e., 3,4- dicarboxylate substituted 6,7-dihydro-1H-azepines 3, 8 and 21, 1,6,7,8-tetrahydroazocines 22, and 6,7,8,9-tetrahydro-1H-azonines 13. Similarly, 2-[(2-thienyl)ethynyl]-4,5,6,7-tetrahydro-1H-azepine 9 is converted into 2-[(2-thienyl)ethynyl]-6,7,8,9-1H-azonine-3,4-dicarboxylate 10 which was characterized by X-ray structure determination. The eight- and nine-membered azaheterocycles 22 and 13, which have not been isolated, undergo thermal isomerization at elevated temperatures. Thus, ring contraction by a 6π-electrocyclic reaction takes place for N-methyl substituted azonine 13, while the N-allyl moiety of azocines 22 engages in an intramolecular Diels-Alder reaction or a 1,7- electrocyclization reaction

2,4-Dichloro-, 4,6-dichloro-, 2,4,6-trichloro- and tetrachloropyrimidine undergo nucleophilic displacements by 4-(dimethylamino)pyridine to give (pyrimidine-2,4-diyl)-1,1’-bis[4-(dimethylamino) pyridinium] dichloride, (pyrimidine-4,6-diyl)-1,1’-bis[4-(dimethylamino)-pyridinium] dichloride, (pyrimidine-2,4,6-triyl)-1,1’,1”-tris[4-(dimethylamino)pyridinium] trichloride, and (5- chloropyrimidine-2,4,6-triyl)-1,1’,1”-tris[4-(dimethylamino)pyridinium] trichloride, respectively. Nucleophilic substitutions of the pyridinium substituents by O- and S-nucleophiles to functionalized pyrimidines are examined

The reaction of methyl 4,6-O-benzylidene-2-deoxy-α-D-erythro-hexopyranosid-3-ulose (1) with ethynylmagnesium bromide in tetrahydrofuran and subsequent trimethylsilylation yielded the methyl 4,6-O-benzylidene-2-deoxy-3-C-ethynyl-3-O-trimethylsilyl-α-D-ribo-hexopyranoside (3). Push-pull functionalization of 3 with N,N,N′,N′,N″,N″-hexamethylguanidinium chloride under basic conditions and following deprotection afforded the spiro{2,5-dihydro-3-dimethylamino- furan-2,8’-4’,4’a,6’,7’,8’,8’a-hexahydro-6’-methoxy-2’-phenyl-pyrano[3,2-d][1.3]dioxine}- 5-ylidenemalononitrile (9). Furthermore, compound 1 reacted with N,N-dimethylformamide dimethylacetal to furnish methyl (E)-4,6-O-benzylidene-2-deoxy-2-dimethylaminomethylene-α-Derythro- hexopyranosid-3-ulose (10). Treatment of 10 with methylhydrazine and amidines yielded (4S,5aR,8R,9aS)-2,5a,6,9a-tetrahydro-4-methoxy-2-methyl-8-phenyl-4H-[1,3]dioxino[4’,5’:5,6]- pyrano[4,3-c]pyrazole (11a) and (2R,4aR,6S,10bS)-4,4a,6,10b-tetrahydro-6-methoxy-2-phenyl- [1,3]dioxino[4’,5’:5,6]pyrano[4,3-d]pyrimidines 12, respectively

Various aplysinopsin and β -carboline thiohydantoin analogues were prepared starting from ethyl 3-formyl-1H-indole-2-carboxylate by condensation with the active methylene group of 2-thiohydantoin, rhodanine, or thiobarbituric acid derivatives

Various 2-substituted 5-methoxy-4-benzyloxazoles 6 and 9 were obtained from tyrosine and m-tyrosine derived amides 5 and 8 by treatment with phosphoryl chloride. A mechanism is proposed in order to explain the observed steric effects of the substituents in 2-position

3-Oxo-2,3-dihydrobenzo[b]furans, -thiophenes and -selenophenes 1a - c afforded the bromo-aldehydes 2 under Vilsmeier-Haack-Arnold conditions. Palladium-catalysed aryl-aryl coupling of 2 with o-formyl-phenylboronic acid allowed the formation of dialdehydes 3 which underwent McMurry cyclisation or pinacol condensation to yield polycyclic aromatic derivatives 4 or the dihydroxylated compounds 5

The 3,4-substituted 2-oxo-piperazines 5 - 9 are obtained by [3+2] cycloaddition from nitrone 1 and a variety of alkenes. Subsequent functionalization of the bicyclic adducts involves reductive N-O bond cleavage. A route towards libraries of immobilized 1,3-aminoalcohols with a 3,4-substituted 2-oxo-piperazine scaffold is briefly discussed for adducts derived from N-substituted maleic imides

Employing three different syntheses a broad spectrum of 4H-imidazoles 3a - 3s has been synthesized. In the course of the two-fold aminolysis reaction leading to derivatives 3q - 3s, deeply colored byproducts could be isolated and structural characterized.These novel donor-acceptor derivatives of type 7 consist of an 1H- and 4H-imidazole which are connected by a nitrogen bridge and rearrange via rapid 1,3-/1,5-hydride shifts. Using 1 H NMR experiments the aminolysis product 3p shows prototropic isomers which could be detected in equilibrium for the first time. Cyclovoltammetric measurements of a series of substituted 2-aryl derivatives 3d - 3i displayed two reversible single electron transfer steps with relatively small semiquinone formation constants between 10 2 and 4×10 3 . The 4H-imidazole 3d was successfully converted into boratetraaza-pentalene 8a, which showed two well separated reduction potentials. The value of semiquinone formation constant of 8a (1.8×10 15 ) is even higher than those reported for similar derivatives. 4H-imidazoles can also be employed for the efficient complexation of catalytically important metals as exemplified by copper complexes 11 and 12. Derivative 3m, which possesses an additional chelating pyridine substructure, formed a stable complex of structural composition Zn(3m)2 with diethyl zinc

The reagent system formed from tris(dichloromethyl)amine (5) and aluminium chloride allows the formylation of aromatic compounds. The scope of the method is comparable with that of the Olah formylation and the Groß-Rieche procedure, since benzene and even chlorobenzene can be formylated. One formyl group is transferred from 5 to the aromatic nucleus. In order to find optimal reaction conditions, the molar amounts of aromatic compounds, 5 and aluminum chloride were varied as well as reaction temperatures and solvents. The activation of 5 with other Lewis acids is also described

Interaction of β -thiocyanatovinyl aldehydes with N-amino heterocycles leads to formation of α, β - unsaturated hydrazonium salts dependent on the functional surroundings. The latter can undergo further intramolecular cyclocondensation giving rise to N,N′-linked isothiazolium salts as the final product. The isolated hydrazonium salts, not undergoing ring formation, have s-trans conformation of the azadiene system

The cyclization of a ribose-derived pentenose oxime with various halogen electrophiles showed bromine to be the most effective reagent, leading to 80% of L-lyxo/D-ribo-pyrroline N-oxides in an 84:16 diastereomeric ratio. In order to explore the scope of this facile process, several other γ,δ - unsaturated oximes were submitted to this reaction. Depending on the substitution pattern, 23 - 87%, yields of pyrroline N-oxides of were registered. With α-allyl-β -ketoester oximes the alkoxycarbonyl group proved a similar (ethoxy) or even better (t-butoxy) trapping nucleophile, leading preferentially to the corresponding bromolactone oxime. - With 2,2-dimethyl-3-butene aldoxime, the corresponding 3-bromopyrroline N-oxide was formed, due to a formal, unusual N-endo cyclization to the chain terminus. This was exploited for a new access to six-membered nitrones from a γ,δ -pentene aldoxime, with addition of Br/OH to the C=C of the 4-pentenal first, and oximation/cyclization following then

The Mannich reaction of 7-aryl-5,6-dihydropyrido[2,3-d]pyrimidines 3, easily accessible by condensation of 6-amino-1,3-dimethyluracil (1) with Mannich bases 2a - c, gives rise to a mixture of 7-aryl-6-(N,N-dimethylaminomethyl)pyrido[2,3-d]pyrimidines 6 and 7 as well as 1,2-bis- (7-arylpyrido[2,3-d]pyrimidin-6-yl)ethane 13 the ratio of which depends on the reaction conditions and the amine used. 6-Alkylamino-1,3-dimethyluracils 15 - 18 were converted to the corresponding 5-(3-oxo-3-phenylpropyl)uracils 19 - 22 by condensation with the Mannich base 2a. Ring closure of 19 - 22 was performed by Vilsmeier formylation to afford the 8-alkyl- and 7,8-diaryl-5,8- dihydropyrido[2,3-d]pyrimidine-6-carbaldehydes 9 - 12 via the corresponding iminium salts 27 - 30