Polar effects in free-radical reactions. New synthetic developments in the functionalization of heteroaromatic bases by nucleophilic radicals

The synthetic interest of the direct substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals is furtheron developed by the following new achievements: i) utilization of the redoc system

in several solvents; ii) utilization of benzoyl peroxide in alcohols; iii) carbamoylation by HCONH₂ and H₂O₂ in the presence of catalytic amounts of Fe(II). These systems allow to obtain either substitution till now tried without success or reactions of industrial interest. Polar effects play a dominant role in determining reactivity, selectivity and synthetic applications; in particular the role of the strongly nucleophilic intermediate radicals of pyridinyl type in the rearomatization step is emphasized.     

Conductive cooling of magmatic intrusions: Short calculation models

Summary We propose some approximate, expedite models for calculating the conductive cooling of magmatic intrusions. At great depths, conduction can account for more cooling than convective phenomena, for tens of thousands of years. Numerical simulation of the thermal development of a region by explicit Euler method requires an appropriate proportion between the quantizations of time and space. Only thus can a numerical solution be obtained, which is consistent and stable, and which conforms to the second law of thermodynamics. In order to account for the geometry and volumetric limits of actual intrusions, we resorted to cylindrical representations rather than to the Cartesian ones used in the references Work conducted at the Naval University Institute of Naples under a 1985 grant from the Ministry of Public Education.     

Hypervalent iodine as good leaving group: oxidative rearrangement of 1-IODO-2-methoxy-2-arylalkanes.

A new example of the good leaving group properties of hypervalent iodine is reported: oxidative rearrangement of 1-iodo-2-methoxy-2-arylalkanes 1 (R=alkyl) provides, via 1,2-aryl shift, alkyl benzyl ketones 3 in good yields.     

Fast atom bombardment positive-ion mass spectra of 1,2,2-tris(sulfonyl)hydrazines

Several 1,2,2-tris(sulfonyl)hydrazines, conceived as prodrugs of 1,2-bis(sulfonyl)hydrazines and synthesized as potential antineoplastic and trypanocidal drugs, were analyzed by mass Spectrometry as part of the confirmation of the structure of these compounds. Since these compounds showed activity against several transplanted animal tumors, an understanding of the mass spectral behavior of these agents is important to gain information should clinical trials and metabolic studies be undertaken. In all spectra, protonated molecular ions were observed. Collision activation resulted in considerable fragmentation in the fast atom bombardment spectra. Rearrangement ions formed by elimination of substituted diimides from the middle of the molecule were observed. Other rearrangements involving the alkyl substituent and sulfonyl oxygen also occurred.     

Synthesis of Anti-Inflammatory α-Arylalkanoic Acids by 1,2-Aryl Shift. New Synthetic Methods (42)

α-Arylalkanoic acids have acquired importance as anti-inflammatory agents and are now in great demand on the pharmaceutical front. Hence, the need has arisen for new and improved, economical synthetic procedures suitable for their preparation and manufacture on an industrial scale. For many years the synthetic approach to this class of compounds was restricted to the Willgerodt and Darzen reactions. More recently, several methods have been developed which are based on the 1,2-aryl shift in acetals of α-functionalized alkyl aryl ketones. This new approach starts from the oxythallation of alkyl aryl ketones first described by Taylor and McKillop in 1971. Asymmetric syntheses of some important arylakanoic acids have also been developed on this basis. The highly toxic thallium salts may be replaced, inter alia, by catalytically effective metal salts.