Mixed Yamaguchi

Use of 2,4,6-trichlorobenzoyl chloride, Et3N, and DMAP, known as the Yamaguchi method,128 is frequently used to effect macrolactonization. The reaction is believed to involve formation of the mixed anhydride with the aroyl chloride, which then forms an acyl pyridinium ion on reaction with DMAP.129... 

Kanda, T., Shirota, O., Ohtsu, Y., and Yamaguchi, M., Synthesis and characterization of polymer-coated mixed-functional stationary phases with several different hydrophobic groups for direct analysis of biological samples by liquid chromatography, /. Chromatogr. A, 722, 115, 1996. 

To complete the synthesis of 1, the acid 3 derived from 20 was converted to the mixed anhydride (Yamaguchi coupling), then esterified with 2. Exposure to , < 8-crown-b gave the all-E tetraene, which was deprotected to give the aglycone 4. 

Fig. 6.4 CdS deposits obtained on a Mo mesh after electrolyses at-0.65 V (vs. SCE) for 3 h in a 0.05 M CdCl2 + 0.1 M TAA aqueous mixed solution (initial pH = 2.0) maintained at 70°C TEM photographs observing the hexagonal particle from its side (a), high magnification image of the same particle (b), and complementary selected area electron diffraction pattern (c). (From K. Yamaguchi et al., J. Phys. Chem. B, 102, 9682 (1998))...

The Yamaguchi Esterification allows the mild synthesis of highly functionalized esters. After formation of a mixed anhydride between the Yamaguchi Reagent (2,4,6-trichlorobenzoyl chloride) and the carboxylic acid, the volatiles are removed and the reaction of the anhydride with an alcohol in presence of a stoichiometric amount of DMAP generates the desired ester. 

Macrocycles are often not easy to form, especially when they include many substituents. The applied procedure to synthesize macrolactones was introduced by Yamaguchi and co-workers and has since been used extensively.21 First the acid is transformed into the mixed anhydride 26. Refluxing the anhydride in toluene will yield the desired macrocycle. The attack of the alcohol at the trichlorobenzoic acid carbonyl moiety is not favored because of steric hindrance by the chlorine substituents ortho to the acid. Therefore the ring is closed selectively. Usually in macrocyclizations high dilution conditions are applied, too, in order to avoid intermolecular reactions. 

Physical methods are of limited effectiveness for separating the phases in cement clinker because of the intimate scale on which the latter are mixed however, Yamaguchi and Takagi (Yl) had some success with the use of dense liquids. Some concentration of the ferrite phase can be effected by magnetic separation (M35,Y1). 

A mild method for forming ter/-butyl esters is the Yamaguchi esterification, which involves reaction of a carboxyl group with 2A6-trichlorobenzoyl chloride and triethylamine in THE The resultant mixed anhydride intermediate reacts with rm-butyl alcohol in the presence of DMAP to give the ferf-butyl ester in good yield.96... 

Zwanenburg and coworkers [38] modified the Yamaguchi procedure in the synthesis of the 12-membered macrolide patulolide C 61). Mixed 2,6-chloro-benzoic anhydride, instead of mixed 2,4,6-trichlorobenzoic anhydride, was used. 

Kuroki, H., and Yamaguchi, K., Combustion synthesis of Ti/Al intermetallic compounds and dimensional changes of mixed powder compacts during sintering. Proceedings of the First US-Japanese Workshop on Combustion Synthesis, Tokyo, Japan, 23 (1990). 

A variety of synthetic methods have been introduced for macrolacto-nizations. The most popular method seems to be the Yamaguchi-Yonemitsu reaction using 2,4,6-trichlorobenzoyl chloride (TCBC) for acid activation by the formation of mixed anhydrides. 

The fust important test of this methodology came in Hanessian s investigation of the spiroketal portion of avermectin Bu- This highly convergent approach incorporates all the oxidation levels and functionality required for carbons C(15)-C(28), except for the necessity of alkyne to alkene conversion. The lithium alkynide was prepared at -78 C and then mixed with boron trifluoride etherate under the conditions of Yamaguchi (Scheme 19). (Direct condensation of the lithium salt and lactone lead to substantial amounts of a, -unsaturated lactone.) Addition of the lactone in stoichiometric amounts to the solution of the modified alkynide led to the formation of the desired hemiketal in acceptable yield. Further improvements could be obtained by the recycling of starting material. ... 

The formation of mixed anhydrides, which in some cases may be isolated, is an established method. For instance, racemic zearalenone (352) has been obtained by treating the seco-acid (351) with trifluo-roacetic anhydride (equation 126). Similarly, antimycin A3 has been prepared. A more modem procedure makes use of Yamaguchi s 2,4,6-benzoyl chloride esterification. For example, a synthesis of methynolide is based on the lactonization of the alkynic seco-acid (353) to (354 equation 127). 

The stereocontrolled total synthesis of (-)-macrolactin A, a 24-membered macrolide, was achieved by J.P. Marino and co-workers/ The key macrocyclization step was carried out using the Yonemitsu modification of the Yamaguchi macroiactonization. In this procedure, the mixed anhydride is added to the highly dilute solution of DMAP rapidly (in one portion) at room temperature. The final step of the total synthesis was the removal of the protecting groups under acidic condition. 

Inanaga, J., Hirata, K., Saeki, H., Katsuki, T., Yamaguchi, M. A rapid esterification by mixed anhydride and its application to large-ring lactonization. Bull. Chem. Soc. Jpn. 1979, 52,1989-1993. 

Studies performed by Rigby and Hutton [29] yield essentially the same results as reported by Yamaguchi. Their experimental procedure consisted of fabricating six samples ranging in composition from 100% silica—0% alumina to 0% silica-100% alumina with increments of 20% silica and alumina. Each fired silica-alumina specimen was ground, and 100 parts of each specimen were mixed with 42 parts of sodium carbonate. The mixtures were pressed into cylinders and subjected to successive 3-h heat treatments at temperatures beginning at 800°C and continuing to 1600°C. 

The mechanism for the formation of metal hydroxide surface precipitates is not clearly understood. It is clear that the type of metal ion determines whether metal hydroxide surface precipitates form, and the type of surface precipitate formed (i.e., metal hydroxide or mixed metal hydroxide) is dependent on the sorbent type. The precipitation could be explained by the combination of several processes (Yamaguchi et al., 2001). First, the electric field of the mineral surface attracts metal ions (e.g., Ni) through adsorption, leading to a local supersaturation... 

I. C. Yamaguchi, K. Shibatani, Y. Suzuki, K. Yamazaki, Y. Komuchi, H. Onishi, and H. Fujimura. Anti-inflammatory actions of proteases, bromelain, trypsin and their mixed preparations (original in Japanese). Nippon Yakurigaku Zasshi 75 227 (1979). 

Yamaguchi, S. and Kunieda, H. (1997) Determination of a three-phase tie triangle (the hydrophile-lipophile balance plane) in a composition tetrahedron Evaluation of the composition of adsorbed mixed-surfactant and the monomeric solubilities of short-chain surfactant. Langmuir, 13, 6995-7002. 

Yamaguchi and co-workers then screened a number of acid chlorides for the formation of the mixed anhydride with two features in mind (1) the component should be a good leaving group, and (2) the carbonyl group of the component should be sterically hindered from nucleophilic attack.5,6 Eventually, 2,4,6-trichlorobenzoyl chloride was deemed to be the best in terms of rate of reaction and yield. 

Kanda, T. Kutsuna, H. Ohtsu, Y. Yamaguchi, M. Synthesis of polymer-coated mixed-functional packing materials for direct analysis of drug-containing serum and plasma by high-performance liquid chromatography. J.Chromatogr.A, 1994, 672, 51-57 [serum plasma direct injection column temp 40 also carbamazepine, chloramphenicol, indomethacin, phenobarbital, phenytoin, theophylline]... 

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