2.5- Dimethyl furan

Scheme 6.39 Generation ofl62 by -elimination from 1 -bromo-1,4-cyclo-hexadiene (174), trapping of162 by furan and 2,5-dimethyl-furan and deprotonation of162 by KOtBu.

In order to establish the general validity of the mechanism of photosensitized oxygenation reactions, substrates other than 2,5-dimethyl-furan have been investigated.81 The quantum yield of product formation is given by the general equation... 

Note Values are obtained by time-resolved measurements at 1270 nm (this work), kg values are given in 10s M-1/sec. a DMF = 2,5-dimethyl furane. 

Several S-substituted furans have been identified from Halliard reaction mixtures which possess meaty aromas including 3-mercapto-2-methylfuran and 3-mercapto-2,5-dimethyl furan (38). 

Cation 6 adds to furan, pyrrole, thiophene and some of their 2,4-dimethyl derivatives bearing a free a-position, in MeCN as solvent. Furan is the least reactive substrate giving 2-arylated product in 32% yield, whereas under the same reaction conditions the sulfur analogue provides 54% of 2-substituted-thiophene 9c (Scheme 10.37). Pyrroles are the most reactive heterocycles, and 2-arylated products 9a-b are found with 64% and 75% yields using pyrrole and 2,4-dimethyl-pyrrole, respectively. Only with 2,5-dimethylated furan and pyrrole, will arylation... 

Furan undergoes phenylation rather than diazo coupling on reaction with benzenediazonium salts, and thiophene similarly yields 2- or 2,5-diaryl derivatives rather than coupled products (see Section 3.3.1.7.2). However, 2,5-dimethyl-furan and 2-/-butylfuran give normal coupled products with the 2,4-dinitrobenzenediazonium ion. 

Acetyl-2,5-dimethyl Furan 643 Benzyl Propionate 661 Type... 

Acetyl-2,5-dimethyl Furan View F avor Chemjca ... 

Incorporation of a furan moiety as a carbene wingtip group was introduced by Nielsen et al. The synthesis is facile enough starting with a bromination (NBS) of 2,5-dimethyl-furan and subsequent reaction with two equivalents of N-substituted imidazole to yield a bis-imidazolium furan [187] (see Figure 3.67). 

Heat transforms ketoacids to methylketones like 2-heptanone, 2-nonanone with a green fatty metallic blue cheese note. Hydroxyy acids form the corresponding lactones. The creamy, buttery, coconut-like 5-decanolide, 4-dodecanolide, 5-dodecano-lide contribute to the sweet creamy buttery flavour in cream and butter. Lactose undergoes a caramelisation reaction to develop sweet, caramelic maltol and 4-hy-droxy-2,5-dimethyl-furan-3(2H)-one. Lactose and milk proteins react in a Maillard reaction to roasted, nutty, burnt notes such as 2,5-dimethyl pyrazine. 

The highly reactive bicyclo[3.1.0]hex-l(5)-ene has also been trapped with 2,5-dimethyl-furan. ... 

Zur Herstellung von 3-Acetyl-5-methyI-l-(4-nitro-phenyl)-lH-pyrazol aus 2,5-Dimethyl-furan und 4-Nitro-phenyldiazonium-chlorid s. Bd. X/3, S. 544 (1965). In einigen Fallen (s.u.) ist der Einsatz von 4-Nitro-phenyldiazonium-tetrafluoroborat in 1,4-Dioxan vorteilhaft2135. 

Fig. 5. Hydrogenation of the ring of heterocyclic compounds using 1 g. of 5% Rh on AI2O3 powder as catalyst and 100 ml. solvent. 1) 1 ml. pyridine, H2O 2) 1 ml. pyrrole, HOAc 3) 1 ml. 2, 5-dimethyl-furane, HOAc 4) 1 g. furoic acid, H2O 5) 1 ml. furfuryl alcohol, H2O.

FIGURE 27-20 Microfabricated columns (a) and chromatogram (b). The columns in (a) were 0.9-m-long spiral and serpentine channels, The mixture (b) was 1, acetone 2. 2-butanone 3. benzene 4, trichloroethylene 5. 2,5-dimethyl-furan and 6. toluene. Air was used as the carrier gas with an outlet pressure of 0.5 atm. (From R. Sacks, in Modern Practice of Gas Chromatography, R. L. Grob and E. F. Barry, eds., 4th ed New York Wiley-Interscience. 2004. p. 269. With permission.)... 

Elaborate kinetic analyses of the photo-oxygenation of 2,5-dimethyl-furan (22, 56) and allylthiourea (40) sensitized by xanthene dyes and chlorophyll, respectively, and of the direct photo-oxygenation of anthracene and 9,10-diphenylanthracene (41) have revealed that Type II direct and indirect (sensitized) photo-oxygenation reactions proceed with... 

Singlet oxygen reacts with fiufuryl alcohol (a 1,3-diene) and 2,5-dimethyl furan (also used as a probe) in what is termed by the organic chemist as a Diel s-Alder reaction to produce an endoperoxide that reacts further to give the products illustrated. The reaction with an alkyl substituted alkene involves abstraction of the allylic hydrogen and recombination to form an... 

Furan derivatives. Acetic anhydride added to a stirred soln. of 2,5-dimethyl-furan in benzene, then a soln. of SnGl4 in benzene added during 30 min. at 15-20°, stirring continued 1 hr. at the same temp. 3-acetyl-2,5-dimethylfuran. Y 87%. P. H. Williams et al.. Am. Soc. 82, 4883 (1960). 

A detailed kinetic model, based on quantum chemical calculations for the initial 2,5-dimethyl furan (2,5-DMF) consumption and important reactions of intermediates, is proposed for the oxidation of 2,5-DMF. The model is validated by comparison with new measurements of 2,5-DMF shock tube ignition delay time and its pyrolysis speciation measurements (/. Phys. Chem. A, 102, 10655 (1998))." " ... 

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