Fujiwara reaction

Hydroarylation, (addition of H-Ar, Ar = aryl), of alkynes, catalysed by Pd(OOCCH3)2 or Pd(OOCCFj)j in acetic acid, is an atom-economic reaction, giving rise to substituted c/i-stilbenes (Fujiwara reaction). Catalytic conversions and improved chemoselectivity to the mono-coupled product under mild conditions can be achieved by modification of the metal coordination sphere with NHC ligands. Hydroarylation of mesitylene by ethylpropiolate (Scheme 2.19) catalysed by complex 107 (Fig. 2.18) proceeds in good conversions (80-99%, 1 mol%) under mild conditions at room temperature. 

It is desirable to have means to measure organohalides such as carbon tetrachloride in situ in water and other environmental media. One approach to doing this has been demonstrated by the in situ analysis of chloroform-contaminated well water using remote fiber fluorimetry (RFF) and fiber optic chemical sensors (FOGS) (Milanovich 1986). With this approach, fluorescence of basic pyridine in the presence of an organohalide (Fujiwara reaction) is measured from a chemical sensor immersed in the water at the end of an optical fiber. Carbon tetrachloride undergoes a Fujiwara reaction, so its determination might be amenable to this approach. 

The Reissert reaction exemplifies the B pathway (equation 73), and is of course a notable method for aldehyde and alkaloid synthesis. The Fujiwara reaction (81JOC3175), a colour test, provides an example of Type D behavior (Scheme 50). 

Ikeda, M. Ohtsuji, H. (1972) A comparative study of the excretion of Fujiwara reaction-positive substances in urine of humans and rodents given trichloro- or tetrachloro-derivates of ethane and ethylene. Br. J. ind. Med., 29, 99-104... 

Fujiwara Reaction Palladium-catalyzed Hydroarylations of Alkynes and Alkenes... 

Quantification. Ultraviolet Spectrophotometry. In blood or urine trichloroethanol (modified Fujiwara reaction)—A. J. McBay e/ al., J. analyt. Toxicol., 1980, 4, 99-101. 

Henshaw J M, Burgess L W, Kowalski B R, Smilde A and Tauler R 1994 Multicomponent determination of chlorinated hydrocarbons using a reaction-based chemical sensor. 1. Multivariate calibration of Fujiwara reaction products Anal. Chem. 66 3328-36... 

Figure 18-3. Comparison of two configurations for a fiber-optic probe for chlorinated hydrocarbons based on the Fujiwara reaction. From [6],...

In the Fujiwara reaction chlorohydrocarbons react with pyridine (N-alkylation) under complete destruction of the ring. But the reaction path will go through a number of Schiff base intermediates, which, depending of the kind of analyte, have different life times and absorbances in the visible range. Thus mixtures of 1,1,1-trichloroethane, trichloroethylene, and chloroform could be resolved, even in the presence of unknown interfering substances. 

Fujiwara reaction Chiorinated hydrocarbons The red colored products of the reaction with the reagent (pyridine, water, base) were detected at different wavelengths using optical sensors... 

In 1972, Heck showed, independently, that aryl, benzyl and styryl halides would react with alkenes in the presence of a hindered amine as organic base at a lower reachon temperature of 100 °C (Scheme 1.16) [51, 66]. A detailed overview on the modem aspects of Mizoroki-Heck reactions, as well as their oxidative variants (Fujiwara reactions), is provided by Martin Oestreich and Verena Trepohl in Chapter 7. 

Fujiwara, Y. and Kitamura, T. (2005) Fujiwara reaction palladium-catalyzed hydroarylations of alkynes and alkenes, in Handbook of C-H Transformations (ed. G. Dyker), Wiley-VCH Verlag GmbH, pp. 194-202. 

These reactions are Moritani-Fujiwara reactions, Heck reactions, Mizoroki-Heck reactions, Kumada-Tamao-Corriu reactions, Murahashi reactions, Eto-Hagihara reactions, Negishi reactions, Migita-Kosugi-Stille reactions, Suznki-Miyanra reactions, and Hiyama reactions. 

An important route for the C-H activation of arenes and heteroarenes is through electrophilic metallation of an aromatic ring, followed by reaction with an alkene. There are numerous simple examples with arenes and heteroarenes reacting with alkenes under palladium catalysis." This has been referred to as the dehydro-genative Heck reaction and the oxidative Heck reaction, as well as the Fujiwara reaction, or Fujiwara-Heck reaction. Both benzene 3.4 and its derivatives (Schemes 3.6 and 3.7) and heteroarenes (Schemes 3.8 and 3.9) can be used. While the reaction has been carried out with a stoichiometric amount of palladium, catalytic processes, with an added oxidant are widespread. 

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