And the Duff reaction

Hydroxy benzo[6]thiophene-4-carboxaldehyde, which is prepared from 5-hydroxybenzo[6]thiophene by the Duff reaction 338 or, better, by a modified Gattermann reaction,340 reacts with diethyl bromo-malonate to give the thienobenzofuran (282), and undergoes the Perkin reaction to give the thienobenzo-a-pyrone (283).338... 

The Sommelet reaction, also known as the Sommelet oxidation, is the oxidation of benzyl halides (1) to the corresponding aldehydes (3) using hexamethylenetetramine (HMTA) followed by hydrolysis of the hexaminium salt 2.1-3 This reaction is closely related to the Delepine amine synthesis, the Duff aldehyde synthesis, and the Krtihnke reaction (see Section 7.10.3). 

Phenolic aldehydes can be obtained by the Duff reaction, in which the phenol is heated with urotropine, boric acid, and glycerol for 30 minutes at 150-160° 857 the yields are not high (15-20%), but the procedure is simpler and less time -consuming than the Reimer-Tiemann synthesis the products are the ortho-derivatives. Dialkylanilines can be formylated in the same way,858 but here the products are the para-aldehydes. 

Application of the Duff reaction to methyl 5-chlorosalicylate containing methanesulphonic acid by the portion-wise addition of hexamethylenetetramine, maintenance of the reaction mixture initially at 80-90X and finally at 130 C for 5 hours, followed by acidic hydrolysis, furnished the 3-formyl derivative in 77% yield (ref.43). 

The Duff reaction is a formylation method normally used for electron-rich aromatics such as phenols and aromatic amines with the formylating agent being hexamethylenetetramine in the presence of glycerol or acetic acid. Conditions are rigorous and the yields are generally low, but the main value is the occurrence of mainly... 

Environmental Fate. Extensive information is available on the general reactions of isocyanates that may pertain to the environmental fate of HDI (Chadwiek and Cleveland 1981 Kennedy and Brown 1992). However, investigations of the environmental fate of isocyanates have focused primarily on TDI and MDI (Duff 1983, 1985 Gilbert 1988 Holdren et al. 1984). Only one laboratory study was located in the available literature specifically on the ehemieal reaetions of HDI (i.e., bicarbonate buffer-catalyzed hydrolysis) that may be relevant to the environmental fate of HDI in water (Berode et al. 1991). HDI is expected to react relatively rapidly with hydroxyl radieals in the atmosphere and to be rapidly hydrolyzed in water and moist soils and sediment. The signifieanee of atmospheric hydrolysis has not been evaluated. Additional field and laboratoiy studies are needed to adequately eharacterize the environmental fate of HDI in air, water, soil, and sediment. 

Baddour and Blanchet (I) paid particular attention to the possible existence of C2H, C3H, C4H, CH, and CH2 in the equilibrium mixture. They assumed that at temperatures above 3000°K. the equilibrium mixture contained the following species Ci, C2, C3, H, H2, C2H2, C2H, C3H, C4H, C4H2, CH, and CH2, the last two becoming significant above 4000°K. Values of the free energy functions and the equilibrium constants for the 16 reactions were calculated by Blanchet by the method of Bauer and Duff (2). The calculated values necessarily depend upon the values assumed for the heat of formation and may require revision for certain species as new data become available. 

Electrophilic substitution reactions of 5-hydroxybenzo[6]thiophene have been investigated in some detail. The 4-position is the most reactive toward nitration,152 nitrosation,497 bromination,422 and formylation (Duff procedure).338 Dibromination in the presence of acetate ion affords 4,6-dibromo-5-hydroxybenzo[6]thiophene,421,422, 497 and not the 3,4-dibromo derivative, as previously believed.542 Dichlorination similarly affords the 4,6-dichloro derivative,421 and not 4,4-dich loro-4,5-dihydrobenzo[6]thiophen-5-one, as reported earlier by Fries d al.542 An interesting comparison can be made between the behavior of 5-hydroxy benzo[6]thiophene and 2-naphthol in electrophilic substitution reactions. It is clear that both positions ortho to the hydroxyl group in 5-hydroxybenzo[6]thiophene are attacked, in contrast to 2-naphthol, where only the 1-position is attacked even in the presence of an excess of the reagent. Disubstitu-... 

Duff reaction (1, 430). Review. In the clastical procedure highly activated aromatic compounds are converted into their formyl derivatives by treatment with hexamethylenetetramine and glyceroboric acid yields are generally low. Smith finds that a variety of aromatic compounds, including simple hydrocarbons, when treated with hexamethylenetetramine in conjunction with trifluoroacetic acid al reflux temperature (82- 90") arc converted into i mine products which yield aldehydes on hydrolysis ... 

Duff reaction. A new application is the mono- and diformylation of 4-substituted... 

In addition Duff et al. also undertook a quantitative analysis by utilising the large difference in cross-polarisation time for protonated and nonprotonated nitrogen. In a related study a series of resins were examined in which biuret linkages predominated [18]. These were formed by the reaction of formic acid and 4,4 -methylenebis(phenyl isocyanate) (MDI). The principal reactions that occur in the resins are shown in Fig. 15.2.16. 

Enantioselective epoxidation. This effective catalyst (1) is readily prepared in a 70-100 kg scale from the resolved diamine (with tartaric acid), the salicylaldehyde (from formylation of the phenol by Duff reaction), and manganese acetate, followed by anion exchange by treatment with aqueous NaCI. 

When Jacobsen s epoxidation was fully described in 1998-99, the Casiraghi method was abandoned in favour of an even older method discovered in the 1930s by Duff. The remarkable Duff reaction uses hexamethylenetetramine, the oligomer of formaldehyde and ammonia, to provide the extra carbon atom. The now otherwise unknown Duff worked at Birmingham Technical College. Later in 1972, a William E. Smith, working in the GEC chemical laboratories... 

Nevertheless, compared to other formylation reactions, such as the Duff Formylation, Gattermann Aldehyde Synthesis, and Gattermann-Koch Formylation, the Reimer-Tiemann reaetion is the only one that occurs under basic conditions, and in certain cases, it is the only feasible method for the direct formylation, e.g., the formylation of oestrogens. ... 

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