Schmidt reactions mechanism

In the first step of the mechanism, the OH group is converted by the reagent to a better leaving group (e.g., proton acids convert it to OHj). After that, the mecha-nism follows a course analogous to that for the Schmidt reaction of ketones (18-16) from the formation of 71 on ... 

Scheme 41 Mechanism of the azido-Schmidt reaction catalyzed by FeCl3...

Carboxylic acids and esters can also be converted to amines with loss of the carbonyl group by reaction with hydrazoic acid, HN3, which is known as the Schmidt reaction,278 The mechanism is related to that of the Curtius reaction. An azido intermediate is generated by addition of hydrazoic acid to the carbonyl group. The migrating group retains its stereochemical configuration. 

Table 6.6 lists some reactions of the electron in water, ammonia, and alcohols. These are not exhaustive, but have been chosen for the sake of analyzing reaction mechanisms. Only three alcohols—methanol, ethanol, and 2-propanol—are included where intercomparison can be effected. On the theoretical side, Marcus (1965a, b) applied his electron transfer concept (Marcus, 1964) to reactions of es. The Russian school simultaneously pursued the topic vigorously (Levich, 1966 Dogonadze et al, 1969 Dogonadze, 1971 Vorotyntsev et al, 1970 see also Schmidt, 1973). Kestner and Logan (1972) pointed out the similarity between the Marcus theory and the theories of the Russian school. The experimental features of eh reactions have been detailed by Hart and Anbar (1970), and a review of various es reactions has been presented by Matheson (1975). Bolton and Freeman (1976) have discussed solvent effects on es reaction rates in water and in alcohols. 

When the two groups of the ketone are para-substituted phenyls, the product of the Schmidt reaction is usually a nearly equimolecular mixture of the two isomeric amides.806 This result, obtained instead of a preferential migration of the more electron-releasing group, is consistent with a mechanism in which the formation of the intermediate rather than its rearrangement is rate determining. 

The rate of the Schmidt reaction of para-substituted benzoic acids is governed by the electron-releasing character of the substituent, the value of the Hammett p parameter being the same as that needed to correlate product ratios in the related reaction of 1,1-diarylethylenes.807 The latter reaction is believed to go by a similar mechanism. 

In more complex reactions, it may not be as straightforward to determine the reduced mass along the reaction coordinate because the exact reaction mechanism is poorly known. This task can be facilitated by ab initio and empirical force-held software packages with built-in capacities to predict and evaluate reaction coordinates (Schmidt et al. 1993 Gale and Rohl 2003). Once the relevant reduced masses are known, a derivation similar to Urey s (1947) equation for equilibrium isotopic fractionation can be followed, obtaining ... 

Models based on chemisorption and kinetic parameters determined in surface science studies have been successful at predicting most of the observed high pressure behavior. Recently Oh et al. have modeled CO oxidation by O2 or NO on Rh using mathematical models which correctly predict the absolute rates, activation energy, and partial pressure dependence. Similarly, studies by Schmidt and coworkers on CO + 62 on Rh(l 11) and CO + NO on polycrystalline Pt have demonstrated the applicability of steady-state measurements in UHV and relatively high (1 torr) pressures in determining reaction mechanisms and kinetic parameters. 

Schmidt, M., Pahl, R., Srajer, V., Anderson, S., Ren, Z., Ihee, H., Rajagopal, S., and Moffat, K. 2004. Protein kinetics Structures of intermediates and reaction mechanism from time-resolved X-ray data. Proc. Natl. Acad. Sci. USA 101 4799 804. 

Heterogeneous reaction mechanisms range from the very simple to the complex. Many features of the formalism presented in this chapter are illustrated by the catalytic combustion reaction mechanism given in Table 11.1. The surface-reaction mechanism is due to Sidwell et al. [361], which in turn had its origins with the work of Schmidt [173,174] and Deutschmann [96,97,101],... 

SCHEME 4. Proposed reaction mechanism of the Schmidt reaction... 

Consideration of the mechanism has to account for the fact, that hydrazoic acid and dinitrogen is liberated during the course of the reaction. The similarity to the Schmidt reaction is obvious, and it should be mentioned that quinisatine (2,3,4-trioxo-tetrahydroquinoline) reacts with sodium azide and sulfuric acid at 0 °C in moderate yield to give 14 [96TH000],... 

Scheme 11/14. Mechanism of the Schmidt reaction with ketones [77].

A variation of the Schmidt type reaction is the rearrangement of an azidocyc-loalkane, which is formed from the addition of hydrazoic acid to an cycloalkene. This reaction was used in the synthesis of muscopyridine (II/U4), a base isolated from the perfume gland of the musk deer [85]. In this context the reaction of II/115 as a model compound under the conditions of the Schmidt reaction gave a mixture of two compounds which after dehydrogenation yielded 11/116 and 11/117. The mechanism can be explained in terms of the migration of different bonds in the precursor. 

The reaction is a Schmidt reaction and its mechanism closely resembles that of the Beckman and Wolff rearrangements. The final step is deprotonation, followed by tautomerization to the lactam. Note that the alternate lactam formed by migration of the secondary carbon was not found. 

When this method is applied to the polynomial approximation of mechanisms, the function G is the response of the kinetic model calculated using the original detailed reaction mechanism, and (/> is a series of orthonormal polynomials constructed by a Gram-Schmidt orthonormalization process using the data set. The function F, defining the final algebraic model, is constructed in such a way that only the significant members of the summation are considered. 

After consideration of the mechanism of the Schmidt reaction of carboxylic acids (cf. section III.A)the prediction was made and verified that the Curtins rearrangement would be subject to acid catalysis The charge and bond distribution in the substrate can almost certainly be best represented by 1 and protonation (reaction 7) was believed to form 2 in which the positive charge on the nitrogen of the... 

Mirek, J. Mechanism of the Schmidt reaction. Bulletin de TAcademie Polonaise des Sciences, Serie des Sciences Chimiques 002, 10, 421-426. 

Kaye, P. T., Mphahlele, M. J., Brown, M. E. Benzodiazepine analogs. Part 9. Kinetics and mechanism of the azidotrimethylsilane-mediated Schmidt reaction of flavanones. J. Chem. Soc., Perkin Trans. 2 1995, 835-838. 

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