Synthesis, proposed reaction mechanism

Figure 8.3 Proposed reaction mechanism for methanol synthesis on Pd and comparison with gas-phase mechanism surface intermediates are speculative and associated energies are estimates...

Fig. 1. Proposed reaction mechanism between PVA and AN for the synthesis of PVA-g-AN copolymer.

Alkene Synthesis by High-Temperature Industrial Methods 315 Problem-Solving Strategy Proposing Reaction Mechanisms 316 Summary Methods for Synthesis of Alkenes 320 EssentialTerms 322 Study Problems 323... 

Fig. 8. Mechanism steps for the synthesis of methanoi, as used in an example by Happel et at. (1990), The mechanism was proposed by Yarlagadda et al. (1988) and assumes that all steps have a net rate in the indicated direction. The species CH4, Oj, CH,OH, CO, HjO, C2H1, and CH3OCHJ are terminal and all others are intermediates formaldehyde (CHjO) is an intermediate because it is present in small amounts (Happel et al., 1990). [Reprinted with permission from Mavrovouniotis, M. L., and Stephanopoulos, G. Synthesis of reaction mechanisms consisting of reversible and irreversible steps I. A synthesis approach in the context of simple examples . Ind. Eng. Chem. Res. 31, 1625-1637, (1992). Copyright 1992 American Chemical Society.]...

Phenylindole is prepared from the reaction of acetophenone and phenylhydrazine, a method known as the Fischer indole synthesis. Propose a mechanism for this reaction. Hint The reactive species is the enamine tautomer of the phenylhydrazone.)... 

Scheme 3.12 Proposed reaction mechanisms for the synthesis of bicyclic amidine from haloiminium salt...

CH2)40)x C0NH-(CH2)6-NHC0-R-NHC0-(CH2)6-NHC00] Figure 6 Proposed reaction mechanism for PEUAm synthesis. 

The first example of direct enantioselective addition of a C—H bond to a ketone was reported by Shibata and co-workers in 2009 using the cationic Ir/ (S)-Hg-BINAP as the catalyst in the synthesis of a chiral 4-acetyl-3-hydroxy-3-methyl-2-oxindole with 72% ee. Recently, Yamamoto and co-workers developed a cationic Ir/(R,R)-Me-BIPAM catalyzed asymmetric intramolecular direct hydroarylation of a-keto amides 178 affording the chiral 3-substi-tuted 3-hydroxy-2-oxindoles 179 in high yields with complete regioselectivity and high enantioselectivity (84-98% ee). In their proposed reaction mechanism, the aryl iridium complex formed via C—H bond activation is coordinated with the two carbonyl groups of the amide (Scheme 5.65). 

Fig. 2 Proposed reaction mechanism for the synthesis of trifluoromethylated alkenes from potassium vinyltrifluoroborates by photoredox catalysis. Reproduced from ref. 87 with permission from The Royal Society of Chemistry.

Zhong, Y. Abrams, C. F. Lim, P. K. Biphasic Synthesis of Poly(2,6-dimethyl-l,4-phenylo)e oxide) Umg a Surfiice-Active Coiq>ling Catalyst. 2. Process Improvemoits, Additional Kinetic Results, and Proposed Reaction Mechanism. Ind. Ene. Chem. Res. 1995. 34(5), 1529-1535. 

Scheme 12 Proposed reaction mechanism for the synthesis of 3,3 -cyclopropyl spirooxindoles...

Mechanistic investigations can also provide insight into unexpected side reactions. For example, in Ir(III)-catalyzed indole synthesis, Messerle and coworkers noted an unexpected side product, N-vinyhndole, when 2-(2-phenylethynyl)anihne was used as substrate with acetone as the solvent By probing solvent effects, deuterium-labeling experiments, and isolation of dormant species formed in stoichiometric experiments, two possible reaction pathways were considered. In collaboration with Eisenstein [303], these pathways were compared computationally, yielding a proposed reaction mechanism that proceeds via the initial formation of imine between the aniline and acetone solvent, followed by imine nucleophilic attack of coordinated alkyne for indole formation. 

SCHEME 22.44 (a) Synthesis of biaryl compounds from Pd-catalyzed decarboxylative cross-coupling reaction between aryl carboxylic acids and (b) proposed reaction mechanism. 

FIGURE 12.1 Synthesis of /j- -CT-NajCit-CAc proposed reaction mechanism. (See insert for color representation of the figure.)... 

Scheme 19. A proposed reaction mechanism for one-pot synthesis of SC from styrene in the presence of ButNBr.

Feng et al. [104] developed an efficient method combining the advantages of ultrasonication with microwave radiation for the synthesis of polysubstituted pyridines (137) (Scheme 35). The reaction was carried out via a K2CO3-promoted tandem addition/cyclization/hydrogen shift process. The proposed reaction mechanism consists of a Michael addition. 

In 1970, Sato reported the synthesis of dibenzopyrene (122) from 120 or 121 by the irradiation of a low-pressure Hg lamp in the presence of a stoichiometric amount of I2 (Scheme 8.61). The electrocyclization and oxidation of the cyclized product 123 by iodine are expected as the proposed reaction mechanism to give the CDC product 124. 

Reduction of propargyl oxiranes with copper hydride results in a diastereoselective synthesis of a-hydroxyallenes. DFT studies, supported by kinetic investigations, partially validate the previously proposed reaction mechanism and attribute the high... 

For example, in the case of monosaccharide ligands, [MLnl complexes were synthesized with yields of 80-90% by electrolysis of methanol solutions of the ligands with a copper or nickel anode (M) and a platinum cathode, followed by predpitation of products with benzene. In contrast to the electrosynthesis, the chemical synthesis of the same copper chelates from cupric acetate in methanol proceeds with only a 30% yield and yields both [MLal and [M(MeC02)L], In electrosyntheses of this type the proposed reaction mechanisms involve the anodic dissolution of the metal followed by complex formation. 

Although the Pinner pyrimidine synthesis was discovered a century ago only a few reports on the reaction mechanism have appeared. The condensation of acetylacetone, methyl acetoacetate, or dimethyl malonate with acetamidine (6) has been studied by Katritzky et al. and the reaction mechanisms for these processes have been proposed by these authors. Outlined below is the proposed mechanism of the condensation of methyl acetoacetate (4) with acetamidine (6)7... 

H2O2 is found to result in formation of 2-ethylindole (75, 90%). Similarly, other trialkylboranes are successfully employed for the synthesis of 2-alkylindoles. A reaction mechanism through 74 as an intermediate is proposed. 

Propose a mechanism for the following reaction, an important step in the lab oratory synthesis of proteins ... 

The final step in an attempted synthesis of laurene, a hydrocarbon isolated from the marine alga Laurencin glandulifera, involved the Wittig reaction shown. The product obtained, however, was not laurene but an isomer. Propose a mechanism to account for these unexpected results. 

The chloromethylated polystyrene resin used for Merrifteld solid-phase peptide synthesis is prepared by treatment of polystyrene with chloromethyl methyl ether and a Lewis acid catalyst. Propose a mechanism for the reaction. 

Two sequential pericyclic reactions are involved in the following furan synthesis. Identify them, and propose a mechanism for the transformation. 

The following synthesis of dienones occurs readily. Propose a mechanism to account for the results, and identify the kind of pericyclic reaction involved. 

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