Trimethylsilyl-substituted diazoalkanes : I. Trimethylsilyldiazomethane

Trimethylsilyldiazomethane was prepared by the action of aqueous KOH on nitroso-N-(trimethylsilylmethyl)urea. The spectroscopic properties of this stable, greenish-yellow liquid which can be isolated by gas chromatography are discussed. Its reaction with acetic acid gives the expected CH₃CO₂CH₂SiMe₃ in addition to SiC cleavage products, CH₃CO₂CH₃ and CH₃CO₂SiMe₃. Products of the 1,3-dipolar addition of Me₃SiCHN₂ to activated olefins were not very stable, and only the adduct with acrylonitrile was isolated as a pure material Trimethylsilyldiazomethane undergoes Me₃SiCH transfer to olefins, giving trimethylsilyl-substituted cyclopropanes, in the presence of CuCI in benzene, but other products are formed as well. Thus such a reaction with cyciohexenegave anti-7-trimethylsilylnorcarane (65%), syn-7-trimethylsilylnorcarane (7%), cis- and trans-l,2-bis(trimethylsilyl)ethylene (9% and 13%, respectively), and an unidentified Me₃SiCH trimer (2.3%).     

Nitroxydes—XLVII: Nitroxydes isoquinuclidiniques

5 and 7 substituted 1,3,3-trimethyl isoquinuclidines are prepared by the action of ammonia on piperitenone and 4-methyl piperitenone. Reduction of 1,3,3-trimethyl 5-isoquinuclidone, and the different alcohols obtained are described. The nitroxydes obtained by oxidation of these amines exhibit long range couplings.     

Non-rigid molecules : III. Sigmatropism in organometalliic complexes of indene

The effects of π system geometry upon the transition states for sigmatropism in five-membered rings is discussed semi-quantitatively using the PMO theory. Comparison of the results with measured activation energies suggests that the [1, 3] averaging in organometallic indene complexes proceeds via sequential [1, 2] shifts in all those cases examined.     

Metal carbonyl-trifluorophosphine systems : X. Mono-and triruthenium carbonyls

Triruthenium dodecacarbonyl reacts with high pressure PF₃ or with PF₃/CO mixtures to yield two series of compounds. At high PF₃ pressures, the mononuclear species Ru(PF₃)_x(CO)_5−x (x = 5, 4 and 3) are the main products with only traces of Ru(PF₃)₂(CO)₃ and Ru(PF₃)(CO)₄ being found. With high carbon monoxide pressure and less PF₃, the species Ru₃(PF₃)_y(CO)_12−y (y = 0–6) are the main products. It is seen that Ru₃(CO)₁₂ can have up to six CO groups replaced sequentially before the cluster is broken followed by the formation of the mononuclear species. The evidence shows that the Ru(PF₃)_x(CO)_5−x species are stereochemically non-rigid.     

Protonation of metal carbonyl complexes : III. Cyclopentadienyl carbonyl complexes of manganese

Using IR spectroscopy, the phosphine derivatives of cyclopentadienylmanganese tricarbonyl have been shown to undergo protonation in solutions of trifluoroacetic acid and in mixtures of this solvent with methylene chloride, protonation at the metal atom being the most probable. Ease of protonation increases with increasing electron-releasing properties of both the π-ring substituents and the phosphine ligands attached to the manganese atom.     

Dual-wavelength spectrophotometry: Part III. Determination of arsenazo I in arsenazo III

A simple rapid spectrophotometric method for the determination of arsenazo I in the presence of large amounts or arsenazo III by means or a dual-wavelength method is discussed. By proper selection of the combination of two wavelengths, γ1 = 502.0 nm and γ2 = 575.3 nm, arsenazo III can be masked instrumentally even when its concentration varies. By this method about 0.5– 40%of arsenazo I in arscnazo III can be determined very easily and accurately.     

Chemistry of leucomycin-X: Conformational studies on leucomycin

The conformation of leucomycin, a macrolide antibiotic with a 16-membered ring lactone, was examined in solution by IR, NMR and CD spectral analysis. The IR reveals that the five hydroxyls are all involved in intramolecular H-bonding. The NMR of the 16-membered ring lactone forming the aglycone shows that the acetyl-carbonyl at C-3, the allylic proton at C-11 and the aldehyde proton are in close proximity on the lactone ring. CD studies suggest that the conformation of the 16-membered ring lactone, especially around the lactone, is mobile and solvent dependent.     

Massenspektroskopische fragmentierungsreaktionen—III : Das scheinbar anomale verhalten von 3-hydroxytetrahydropyransystemen

Tetrahydropyran derivatives may lose C-2 together with a substituent from C-3 accompanied by ring contraction. This explains why, e.g., compounds derived from 3-hydroxytetrahydropyran sometimes fragment in a manner expected for an isomeric tetrahydrofuran system. The prerequisities for this rearrangement and its mechanism are discussed.     

Steric effects in conjugated systems: III. The nonplanarity of 2,4-dimethylpentadiene-1,3

Based on earlier results of monomethylated butadienes and 2,3-dimethylbutadiene, the conformational analysis of 2,4-dimethylpentadiene-1,3 was performed. The nonplanar conformations of the molecule were found to be more stable than the planar ones and the s-cis-s-trans equilibrium shifted towards a larger amount of s-cis conformer as compared with that in butadiene.     

Effect of perchlorates on the infrared bands of water: III. The structural model

The splitting of OD bands of HDO in the presence of perchlorates is studied and a structural model of solution is proposed. The assignment of D₂O and H₂O stretching bands in perchlorate solutions is discussed and the effect of temperature and of perchlorate on the vibrational bands of water are compared. Two other band-splitting anions are presented and the problem of anion-water hydrogen bonding is analysed.     

Steric effects in conjugated systems: II. 2,3-Dimethylbutadiene

Based on earlier results of conformational analysis by the Wiberg method¹ of monosubstituted methylbutadienes, analogous calculations for 2,3-dimethylbutadiene have been carried out. Contrary to the opinion of Aten et al.² who assumed almost free rotation, the molecule was shown to exhibit a considerable strain which hinders the rotation of methyl groups and lengthens the C_sp²-C_sp² bond compared with the length of the central bond in butadiene. The calculated lengthening agrees qualitatively with that obtained by electron diffraction¹.     

Low-frequency vibrations of molecular solids: XV. Globular molecule 1,2-dichloroethane

The far infrared and Raman spectra of polycrystalline 1,2-dichloroethane and 1,2-dichloroethane-d₄ for the low temperature modification have been measured from 450 to 33 cm⁻¹ at various temperatures from −100 to −182°C. Raman spectra of the high temperature crystalline modification for both samples were also investigated. The Raman data are in conflict with those previously reported. Assignments are made for the lattice vibrations in terms of the crystallographic unit cell C_2h⁵ (P_21/c) with two molecules per unit cell. The spectra of the high temperature modification are consistent with those expected for orientationally disordered crystals.     

Solanum-alkaloide—SCVI: Synthese von solafloridin und 25-iso-solafloridin

3β,16α-Diacetoxy-20-(5-methyl-2-pyridyl)-pregna-5,20-diene (2) available from 3β-acetoxy-pregna-5,16-dien-20-one (1) was transformed into solafloridine (11) and 25-iso-solafloridine (13).     

Etudes photochimiques—XIV : Photoreactions des methylisothiazoles

Photorearrangement of methylisothiazoles proceeds via a zwitterion and the amount of rearranged products increases with solvent polarity. When irradiated in the presence of primary amines, 3-methylisothiazole which is the less isomerised, and 5 methylisothiazole give charge transfer complexes. The amine cation radical is hydrolysed to an aldehyde. 4-Methyl isothiazole does not lead to a charge transfer complex.     

Organogermanium compounds : II. Reduction of organic halides with hydrogermanes

The scope of the reduction of organic halides with trialkylgermanes under homolytic condition has been studied. Germanium hydrides can reduce polyhaloalkane without catalysts under mild conditions, the homolytic mechanism being, however, established for the uncatalyzed reduction. The observed orders of reactivity and selectivity in the reduction are consistent with a radical chain mechanism involving free germyl radicals. Some synthetic applications are described.