cis-Azoxyalkanes. IV. Preparation and nuclear magnetic resonance spectra

Abstract

5158 xz greater than xl, it was possible to submit the isolated product 1 (with [WID) obtained from the experiment with an extent of reaction of XI to a further photolysis under the same conditions. In this way, if a photolysis of reaction extent x' is achieved from this already optically active product l ( [ a l ]~) the remaining product has a new optical rotatory power ([az]D). The corresponding extent of reaction xz of the photolysis starting with (f)-1 is given byThis procedure was also used by Mitchell.z6 We checked that the enantiomeric purity of the remaining compound in the partial photoresolution was the same either by achieving directly the reaction extent XZ, or by achieving x1 and then x ' , separately. This procedure was used in the photolysis of both a-azido-N,N-dimethylpropionamide and camphor.(+)-Camphor. Racemic camphor provided by the Delaire Co. (France) was recrystallized twice from hexane and then sublimed. Its glc analysis showed a purity greater than 99% and the optical activity was [ a I z 6~ -0.14" (c 6, hexane).This racemic camphor was obtained by a synthesis starting from naturally occurring optically active a-pinene and since one of the steps of this synthesis was a racemization, the slight residual optical activity observed in the final product was probably due to incomplete racemization.A sample of camphor ( [ a ]~ -0.14") purified by the above procedure was submitted to preparative glc, and there was no difference in the specific rotation of the highly purified camphor collected. The presence of an optically active impurity was therefore ruled out, so that the slight optical activity observed was due to an enantiomeric excess of 0.25% in the camphor. For our experiments requiring completely racemic material, we adjusted the rotatory power of the nearly racemic compound to [a]D 0.005 f 0.005' by the addition of optically pure (+)-camphor [[aIz51) +52.9" ( c 2.5, hexane)].Partial Kinetic Photoresolution of Racemic Camphor. A solution cis-Azoxyalkanes.Resonance Spectral of 6 g of racemic camphor in 360 ml of n-hexane was placed in the irradiation cell (diameter 100 mm, volume 360 ml) which was closed with a glass stopper and magnetic stirring was maintained during the course of the irradiation. For the determination of the extent of the photodecomposition, 1-ml samples were taken, a known weight of a standard (n-hexadecane) was added, and the mixture was analyzed by glc (column A temperature 120", carrier Nz 25 mlimin); thus, the disappearance of camphor was determined by measurement of the peak areas of camphor and the standard. When the desired extent of reaction had been achieved the irradiation was stopped. The solvent then was carefully removed avoiding sublimation of remaining camphor which was separated from the mixture of photoproducts by preparative glc (column B temperature 145", carrier N 1 100 mlimin). Two such purifications by glc were necessary and the purified camphor was used for the determination of the optical purity. The optical rotatory power was measured in n-hex...

Intramolecular [1,5]sigmatropic alkyl shift in the isoindence system

“…slant rate of exchange of the alkyl group, is equally applicable to reactions of the form shown in eq 3, 4, and 5, provided the dioximato ligands have equal influence on the rate of exchange.11 The latter proviso is supported by the observed random ratio of organocobalt(lll) complexes, II, III, and V in the equilibrium mixture. RCo (dmgH)jpy + Co(dmgH)(chgH)py RCo(dmgH)(chgH)py ^Co(dmgH),py (4) RCo (chgH),py + Co(dmgHl(chgH)py RCo(chgH)(dmgH)pv + Co(chgH)2py (5) (14) The reverse of reaction 3 and the forward and reverse reactions 4 and 5 must similarly be second order. (15) G. N. Schrauzer and E. Deutsch, J.…”

“…Recently, it was demonstrated by Willcott and Rathburn that the thermal [1,5] methyl shift of 1,5,5-trimethylcyclopentadiene was, to a significant extent, an intermolecular process.1 While isomerizations of spirodienes, such as that of the spiro [4,4]nona-l,3-diene system,2 must undoubtedly proceed intramolecularly, Willcott's results raised the question as to whether any potentially intermolecular [1,5] alkyl shift processes are indeed intramolecular. We wish to report at this time the first unambiguous example of such an intramolecular process.…”

A highly efficient iron doped BaTiO3nanocatalyst for the catalytic reduction of nitrobenzene to azoxybenzene

“…Azoxy compounds are versatile organic compounds that have received considerable attention due to their physiological activity and their applications as liquid crystalline materials. [1][2][3][4] Azoxybenzene has been used in dyes, analytical reagents, reducing agents, stabilizers, food additives, pigments, and polymerization inhibitors. [5][6][7][8] The synthesis of azoxybenzene is carried out through the oxidation of aromatic amines and reduction of nitro compounds by using various stoichiometric reagents.…”

Bi–KOH. An efficient reagent for the coupling of nitroarenes to azo and azoxy compounds

“…4 Also, metal catalysed reactions are of interest because of their relevance to the enzymatic degradation of nitrogen-containing compounds in biological synthesis. 5 Recently we have reported the rapid pinacolization of aromatic carbonyl compounds with bismuth and KOH in methanol at ambient temperature. 6 To explore its synthetic utility we have investigated the reductive coupling of nitro compounds with bismuth and KOH in methanol at room temperature and under microwave irradiation (Scheme 1).…”