New methods of free-radical perfluoroalkylation of aromatics and alkenes are reported. n-C(4)F(9)I has been utilized as source of C(4)F(9)(*) radical through iodine abstraction by phenyl or methyl radical. The reaction with alkenes, carried out in the presence of catalytic amount of Cu(OAc)(2), leads to substitution by a mechanism substantially identical to the aromatic substitution and not to the usual chain addition of perfluoroalkyl group and iodine atom to the double bond. This has allowed to measure for the first time the absolute rate constants and the partial rate factors for the homolytic aromatic perfluoroalkylation by competition kinetics. The C(4)F(9)(*) radical shows a clear-cut electrophilic character in the aromatic substitution, as already reported for the addition to alkenes, but the low regio- and chemoselectivities suggest that the polar effect is not the main factor in determining the high reactivity of perfluoroalkyl radicals toward aromatics (10(5)-10(6) M(-1) s(-1), 2-3 orders of magnitude more reactive than alkyl radicals). The enthalpic factor, related to the involved bond energies, appears to be the major cause of the increased reactivity. The polar effect is considered as related more to the polarizability than to the polarity of a radical (the sigma-perfluoroalkyl radicals are considered less polarizable and hence less sensitive to polar effects than pi-radicals).
This is a general overview of some first-, second-and thirdgeneration fine chemicals with origins from the lignin oxidation process. The synthetic organic processes of these substances are presented as well as several applications for the synthesis of a variety of pharmaceutical chemicals.
This report discloses proof of concept and experimental results from a project involving design, development, and investigation of a novel approach for flow chemistry and the realization of equipment operating according to this new approach. This device is named multijet oscillating disk (MJOD) reactor and is dedicated to continuous flow organic synthesis in milliscale. Characteristics such as the importance of the multijet disk unit, with or without oscillating, and possible limitations, such as backmixing, have been explored, and the flow system is benchmarked with other technologies. Several well-known reactions and syntheses usefully both in the chemical industry as well as in the research laboratory have been conducted using the new system, which have been benchmarked with batch-and microreactor protocols. In particular the Haloform reaction, the Nef reaction, nucleophilic aromatic substitution, the PaalÀKnorr pyrrole synthesis, sodium borohydride reduction, O-allylation, the Suzuki crosscoupling reaction, the Hofmann rearrangement and N-acylation were performed during the study of the MJOD reactor performance. Our investigations revealed that the MJOD millireactor system can produce various organic compounds at a high rate concomitant with an excellent selectivity. A Hofmann rearrangement was conducted, a reaction that involves handling of a slurry of the substrate. This reaction was successfully conducted, achieving a quantitative conversion into the target molecule.
New synthetic procedures for vanillin, iso-vanillin, heliotropin, and protocatechualdehyde starting from catechol are described. The utilisation of statistical experimental design and multivariate modelling and the mechanistic interpretation of the acid and base catalysis in the condensation of catechol derivatives with glyoxylic acid and in the regiocontrolled methylation of protocatechualdehyde and of the Cu(II) salt catalysis in the oxidative decarboxylation of mandelic acid derivatives have allowed the development of new highly selective processes.
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