Organometallic complex compounds,part 51. Ligand property controlled CO-insertion in nickel complexes: Separation of electronic and steric effects

Summary The influence of twenty phosphorus-containing ligands on the CO insertion with four-coordinated Ni¹¹ complexes as starting reagents is reported. Quantitative separation of the electronic and steric effects by a multilinear regression analysis (55% electronic and 45% steric influence) is presented together with a three dimensional representation. An increase in donor-capacity favours CO insertion and an increase in steric hindrance leads to a decrease in the fraction of the corresponding ketone.     

Reaktionen mit phosphororganischen Verbindungen, 48. Mitt.

Reaction of the vicinal diols of steroids1, 5, 7, 10, 13, and16 with TPP/DEAD yields both regio-and stereospecifically the oxosteroids2, 6, 8, 11, 14, and15 by displacement of an axial hydrogen and extrusion ofTPPO besides the cholest-4-en-6-ols9 and12 and the cyclic carbonate3. 16, 17-androstandiol16 gives only the cyclic carbonate17. The different structures of the carbohydrates withcis-diol arrangement19 and21 lead exclusively to cyclic carbonates20 and22 in moderate yields. Treatment of1 with TPP/DEAD/HN₃ affords 3-azido-2-hydroxycholestane4 in addition to the above mentioned2.

     

Amide interactions in chlorinated solvents

Enthalpies of solution and of transfer of amides for the solvents chloroform (CHCl₃), methylenechloride (CH₂Cl₂), carbontetrachloride (CCl₄), cyclohexane (C₆H₁₂), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), and ethylacetate (EtOAc) have been used to isolate and quantify the solvation interactions of amides in chlorinated solvents. Specific interactions at the aminde carbonyl and N–H groups have been identified. An analysis of the transfer enthalpies of pyrrole and methylpyrrole from cyclohexane to the chlorinated solvents shows that specific interactions between the pyrroles and these solvents are similar in nature. A means of calculating differences in the transfers of different solutes between the same solvent pair is given.Work done at Lebanon Valley College.     

Enzymatic hydrolysis of heterocyclic nitriles

Chemoselective hydrolysis of heterocyclic nitriles can be achieved by an easy to use immobilized biocatalyst prepared from Rhodococcus sp. Pyrimidine-2-carbonitrile ( 2a ) and 3-chloropyridazine-4-carbonitrile ( 4a ) were converted into the corresponding amides while from 2-ethoxycarbonyl-4-pyridinecarbonitrile ( 1a ), 6-methylpyridazine-3-carbonitrile ( 3a ), 3-chloropyridazine-4-carbonitrile ( 4a ), 3-ethoxycarbonyl-4,5-dihydroisoxazole-5-carbonitrile ( 8a ), indole-3-carbonitrile ( 9a ) and indole-3-ylacetonitrile ( 10a ) the acids were formed.     

The active centres' nature in anionic polymerization of polar monomers

In the anionic polymerization of polar monomers the nature of active centres is considerably influenced by the reaction conditions. In a survey, the present state of knowledge is represented and discussed for the polymerization of acrylonitrile. Analogous problems of methyl methacrylate and vinylpyridine polymerization are included in the considerations.