Polycyclic arenes functionalization

Because C-H bonds are usually less reactive towards dioxirane oxidation than heteroatoms and C-C multiple bonds, it is instructive to give a few general guidelines on the compatibility of functional groups within the substrate to be submitted to oxidative C-H insertion Substances with low-valent heteroatoms (N, P, S, Se, I, etc.), C-C multiple bonds, and C=X groups (where X is a N or S heteroatom) are normally not suitable for C-H insertions, because these functionalities react preferably. Even heteroarenes are more susceptible to dioxirane oxidation than C-H bonds, whereas electron-rich and polycyclic arenes are only moderately tolerant, but electron-poor arenes usually resist oxidation by dioxiranes. N-oxides and N-oxyl radicals are not compatible because they catalyze the decomposition of the dioxirane. Oxygen insertion into Si-H bonds by dioxirane is more facile than into C-H bonds and, therefore, silanes are not compatible. Substance classes normally resistant towards dioxirane oxidation include the carboxylic acids and their derivatives (anhydrides, esters, amides, and nitriles), sulfonic acids and their de-... 

The kinetic data for isomerization of a range of arene oxides in both the mono- and polycyclic aromatic series as a function of pH showed that the process can be acid-catalyzed (kn) in all cases. A pH-independent spontaneous aromati-zation in the neutral to alkaline region (ko) was also found for arene oxides (generally too slow to be observed for K-region arene oxides). The kinetics of these isomerizations obey the rate law ... 

Various reactions discussed so far have been applied to cleave complex vinylcyclopropanes which are available by a novel method of extreme convergency. In 1981 Wender and Howbert reported their first example for an intramolecular 1,3-photoaddition of an olefin unit to an adjacent arene moiety This ingenious strategy generates functionalized polycyclic vinylcyclopropanes in a regio- and stereocontrolled fashion which is perfect to synthesize certain terpenes. The key steps of a short route to a-cedrene are displayed in equation 182. ... 

The peak, which has the same retention time as that of the N-OH product in the AAF profile, may be the N-OH metabolite of Trp-P-2. Detailed chemical characterization of each peak is underway. The similarity of the metabolic profiles of these two carcinogens is not unexpected as they have similar chemical structures. Cytochrome P-450s are known to perform N-hydroxylation, arene oxidation and demethylation(15,16). These functions should not be interfered with by the internaT nitrogens in the polycyclic ring such as those in the Trp-P-2. It is not surprising to see similar metabolic profiles for Trp-P-2 and AAF. 

The reactions of HTIB with alkenes (Scheme 3.73) can be rationalized by a polar addition-substitution mechanism similar to the one shown in Scheme 3.70. The first step in this mechanism involves electrophilic flnfi-addition of the reagent to the double bond and the second step is nucleophilic substitution of the iodonium fragment by tosylate anion with inversion of configuration. Such a polar mechanism also explains the skeletal rearrangements in the reactions of HTIB with polycyclic alkenes [227], the participation of external nucleophiles [228] and the intramolecular participation of a nucleophilic functional group with the formation of lactones and other cyclic products [229-231]. An analogous reactivity pattern is also typical of [hydroxy(methanesulfonyloxy)iodo]benzene [232] and other [hydroxy(organosulfonyloxy)iodo]arenes. 

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