Furan-2-methanethiol

The synthesis of furan-2-methanethiol was described by Reichstein and Staudinger (1928). Furfural (1.63) is converted into furfuryl disulfide (difurfuryl disulfide, 1.136) by treatment with the sulfide or hydrosulfide of an alkaline-earth metal or of ammonia. The disulfide in an alcoholic solution can be reduced, for example, by addition of zinc dust and a small quantity of acetic acid. A method has been described by Kofod (1955). 

This product is easily obtained by methylation of the commercially available furan-2-methanethiol (1.128). 

It was prepared by reaction of furan-2-methanethiol with ethyl iodide. 

The electrophilic propargylation at the C-2-position of furans with propargylic alcohols can be effected by using 5 mol% of the cationic methanethiolate diruthenium complex 41 as a catalyst (Equation 29). Substrates are limited to 1-phenyl-substituted secondary propargylic alcohols <2003AGE1495>. 

CIC The main components, responsible for the repulsive odour are 1-propanethiol, ethanthiol and methanethiol, and the corresponding sulfides. Ethyl butyrate and ethyl-2-methyl butyrate impart the fruity, fresh strawberry character. Components like vanillin, 2,5-dimethyl-4-hydroxy-furan-3(2H)-one, 3-methyl-cyclopent-2-en-2-ol-l-one, gamma-decalactone (all not yet identified in Durian) may support the creamy nutty character. 

The Maillard reaction plays an important role in flavor development, especially in meat and savory flavor (Buckholz, 1988). Products of the Maillard reaction are aldehydes, acids, sulfur compounds (e.g., hydrogen sulfide and methanethiol), nitrogen compounds (e.g., ammonia and amines), and heterocyclic compounds such as furans, pyrazines, pyrroles, pyridines, imidazoles, oxazoles, thiazoles, thiophenes, di- and trithiolanes, di- and trithianes, and furanthiols (Martins et al., 2001). Higher temperature results in production of more heterocyclic compounds, among which many have a roasty, toasty, or caramel-like aroma. 

The application of the Billups approach to l//-cyclopropa[/]phenanthrene requires dehydrochlorination and subsequent double-bond isomerization of l-chloro-la,9b-dihydro-l/7-cyclo-propa[/]phenanthrene (8). The direct double bond migration did not, however, occur in this system, but was achieved indirectly by nucleophilic trapping of the intermediate cyclopropene, la77-cyclopropa[/]phenanthrene (9) with methaneselenolate - or methanethiolate. Base-induced elimination of the dimethylselenonium or dimethylsulfonium derivative 10 did not allow isolation of the expected cycloproparene, but in the presence of furan a mixture of interception products 12-14 derived from l/f-cyclopropa[/]phenanthrene 11 and its la//-isomer 9 was obtained. 

Particularly important substances for the basic flavour of baked and cooked meat are aliphatic thiols (such as methanethiol), sulfides (such as dimethyldisulfide, dimethytrisulfide and dimethyltetra-sulfide), aldehydes (such as acetaldehyde, 2-methylpropanal and 3-methylbutanal), furans, pyridines and thiophenes with a mer-capto group in position C-3 and their corresponding disulfides and some other aliphatic and heterocyclic sulfur compounds. Examples of important aliphatic thiols are 3-mercaptobutan-2-one (8-179) and 3-mercaptopentan-2-one found in cooked beef. A mixture of 3-mercapto-2-methylpentane-l-ol diastereoisomers (Figure 8.86) has a broth-like, sweaty and leek-hke flavour. Very low odour threshold concentrations and an odour reminiscent of roasted meat are found in 2-methylfuran-3-thiol (8-180), which also occurs in beef broth, roasted coffee and other foods, 2,5-dimethylfuran-3-thiol, their corresponding disulfides and 2-furanmethanethiol (furfuryl mercaptan). The typical aroma of roast beef is found in... 

The aroma of potato chips (French fries) is a mixture of more than 500 compounds. The important components are 2,3-diethyl-5-methylpyrazine, 2-ethenyl-3-ethyl-5-methylpyrazine, (2E,4Z)-deca-2,4-dienal, ( )-4,5-epoxydec-2-enal (8-183), l-octen-3-one, (Z)- and ( )-non-2-enal, 2-methylpropanal, 2-methylbutanal and 3-methylbutanal, biacetyl and 4-hydroxy-2,5-dimethyl-2f/-furan-3-one (furaneol). Another principal component is (Z)-2-(methylthiomethyl)but-2-enal (also known as 2-ethylidene methional, 8-198), which arises in the reaction of methional with acetaldehyde. Both isomers of 2-(methylthiomethyl)but-2-enal are used as flavour enhancers. Less signiflcant compounds are methanethiol and methional. 

By a wide margin, Cheddar is the most popular cheese flavor in North America. Its flavor is described as sweet, buttery, aromatic, and walnut, yet there is no general consensus among flavor chemists about the identity of individual compounds or groups of compounds responsible for Cheddar flavor. Reinec-cius and Milo (80) concluded that butyric acid, acetic acid, methional, 2,3-butanedione, and homofuraneol (5-ethyl-4-hydroxy-2-methyl-(2//)-furan-3-one) are primary contributors to the pleasant mild flavor of Cheddar cheese. Important contributors to Cheddar aroma are 2,3-butanedione, dimethyl sulfide/trisulfide, and methanethiol (80). 

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