Rearrangement operator

In cases where a 2-C-(hydroxymethyl)aldose is easily available via base-catalyzed aldolization of a 2,3-0-alkylidene-aldofuranose with formaldehyde, the carbon-skeleton rearrangement operating in the Bilik reaction can also be conveniently exploited for preparation of 2-ketoses. The method is especially advantageous for synthesis of heptuloses and octuloses as (1) in special cases the 2-C-hydroxymethyl side chain construction is simpler than the classical aldose chain elongations, and (2) the equilibrium of a 2-C-(hydroxymethyl)aldose and its corresponding 2-ketose in the Bilik interconversion is much more favorably shifted to the side of the latter sugar (always > 85%) than the LdB-AvE transformation of the pertinent unbranched aldose. 

The Favorskii rearrangement of a-haloketones in the presence of base yields carboxylic acids or carboxylate esters. The intermediate in the classic version of the reaction is a cyclopropanone, but an alternative mechanism, related to that of the benzylic acid rearrangement, operates in other cases, with analogous outcome. 

One way of proceeding is shown in the flow diagram of figure 2 for the ease of = 8, P = 3. The operation labeled PERMUTE rearranges the sequence of data. The /th member is placed into theyth position where] is calculated from i as follows... 

Beckmann Rearrangement. Prepare the 85% sulphuric acid by adding 50 ml. of the concentrated acid cautiously to 10 ml. of water, stirring the mixture meanwhile, and then cool the diluted acid in ice-water. Place 16 ml. of the cold acid in a 500 ml. beaker, add 8 g, of the pure oxime, and warm the mixture cautiously until effervescence begins, and then at once remove the heat. A vigorous reaction occurs, and is soon complete. Repeat this operation with another 8 g. of the oxime in a second beaker the reaction is too vigorous to be carried out with larger quantities. 

The third operation, involving the conversion of the diazo ketone into an acid or a simple derivative thereof, is known as the Wolif rearrangement. 

The last group of reactions uses ring opening of carbonyl or 1-hydroxyalkyl substituted cyclopropanes, which operate as a -synthons. d -Synthons, e.g. hydroxide or halides, yield 1,4-disubstituted products (E. Wenkert, 1970 A). (1-Hydroxyalkyl)- and (1-haloalkyl)-cyclopropanes are rearranged to homoallylic halides, e.g. in Julia s method of terpene synthesis (M. Julia, 1961, 1974 S.F. Brady, I968 J.P. McCormick, 1975). 

Although manufacture of benzidine itself has virtually ceased in Europe and the United States, similar rearrangement processes are operated for 3,3 -dichlotobenzidine [91-94-1J, o-dianisidine (3,3 -dimethoxybenzidine), and benzidine-2,2 -disulfonic acid. 

Maltol. Otsuka Chemical Co. in Japan has operated several electroorganic processes on a small commercial scale. It has used plate and frame and aimular cells at currents in the range of 4500—6000 A (133). The process for the synthesis of maltol [118-71 -8], a food additive and flavor enhancer, starts from furfural [98-01-1] (see Food additives Flavors and spices). The electrochemical step is the oxidation of a-methylfurfural to give a cycHc acetal. The remaining reaction sequence is acid-catalyzed ring expansion, epoxidation with hydrogen peroxide, and then acid-catalyzed rearrangement to yield maltol, ie ... 

Slow-binding inhibitors operate by one of two mechanisms. Either the inhibitor binds slowly in an initial step, or the initial binding step occurs quickly, followed by a slow rearrangement of the E-I complex. 

Several 3-acylamino-l,2-benzisoxazoles such as (278) underwent rearrangement to 3-(o-hydroxyphenyl)-l,2,4-oxadiazoles (279) on heating with base. It has been questioned whether the same mechanism is operative in these last rearrangements (8lAHC(29)l4l, p. 150). 

In case A the solvents are immiscible, so the rate of feed solvent alone in the feed stream F is the same as the rate of feed solvent alone in the raffinate stream R. In like manner, the rate of extraction solvent alone is the same in the stream entering S as in the extract stream leaving E (Fig. 15-12). The ratio of extraction-solvent to feed-solvent flow rates is therefore S /F = E /R. A material balance can be written around the feed end of the extrac tor down to any stage n (see Fig. 15-12) and then rearranged to a McCabe-Thiele type of operating line with a slope of F /S [Eq. (15-11)]. 

As one can notice, the boost-mode converter has the same parts as the forward-mode converter, but they have been rearranged. This new arrangement causes the converter to operate in a completely different fashion than the forward-mode converter. This time, when the power switch is turned on, a current loop is created that only includes the inductor, the power switch, and the input voltage source. The diode is reverse-biased during this period. The inductor s current waveform (Figure 3-4) is also a positive linear ramp and is described by... 

Rearranging for Lp,j and substituting T a = 3(max)//( one ean solve for the maximum primary induetanee using known power supply operating parameters using Equation 3.25 ... 

The rearrangement of 120 g. (1.06 moles) of pure cyclo-hexanoneoxime (Org. Syn. ii, 56) (Note i) is carried out in the following fashion. In a 250-cc. Erleruneyer flask are placed 10 g. of cyclohexanoneoxime and 20 cc. of sulfuric acid (sp. gr. 1.783) (Note 2). The flask is placed on a wire gauze over a small free flame and heated slowly, with occasional shaking, until the first appearance of bubbles. The flame is then removed immediately, and the very vigorous exothermic reaction which occurs is allowed to run to completion (Note 3). This requires only a few seconds. This solution is then poured into a 3-I. round-bottomed flask, and another lo-g. portion of the oxime is introduced into the Erlen-meyer flask and treated with sulfuric acid as before. These operations are repeated until the twelve lo-g. portions have been treated. 

The di-7r-methane rearrangement has been studied in a sufficient number of cases to develop some of the patterns regarding substituent effects. When the central sf carbon is unsubstituted, the di-7i-methane mechanism becomes less favorable. The case of 1,1,5,5-tetraphenyl-l,4-pentadiene is illustrative. Although one of the products has the expected structure for a product of the di-7t-methane rearrangement, labeling with deuterium proves that an alternative mechanism operates ... 

In an idealized situation, the vessel and its jacket each operate continuously under isothermal conditions. Rearranging Equation 7-69 becomes ... 

We can provide an operational definition for the constant by rearranging Equation (14.23) to give... 

Table 7.2 Rearranged activities to improve plant operation ...

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