A part of the "bouquet of wines" can be caused by the presence of odorous heterocycles produced by chemical reactions between S-amino acids and α-dicarbonyl compounds. Under wine ageing physic-chemical conditions (20 ± 2 °C, ethanol/water 12% v/v, pH 3.5), products of the diacetyl (DI) reaction with cysteine include a number of 1,3-N,S and 1-3-N,O 5 member heterocycles having methyl groups attached at C(2). The origin of this methyl-C(2) fragment was not clear; it could be supplied from DI or from cysteine. To explore this question, a parallel reaction was run in which DI was replaced by 3,4-hexanedione. With the C(1) and C(4) carbons of DI thus marked with methyl groups, the product distribution demonstrated that in the DI and cysteine reaction, both DI and cysteine provided the methyl-C(2) to varying degrees in the formation of 2-methylthiazole, 2-methyl-3-thiazoline and 2,4,5-trimethyloxazole but only cysteine supplied this fragment for 2-methylthiazolidine. The results are interpreted in terms of reaction paths appropriate for the mild conditions. These pathways shed light on the mechanisms leading from dicarbonyls to heterocyclic compounds. Like all the chemical pathways, they anticipate the impact of other compounds and physicochemical parameters on heterocyclic generations the generation of heterocyclics. They also suggest the presence of unexplored odorous compounds.

The Diels–Alder reaction of various pyrimidine ortho-quinodimethanes generated in situ with C60 gives access to a variety of new fullerodihydroquinazoline derivatives. This variety is increased since substituents on the pyrimidine ring can be easily modified before or after its reaction with C60. Variable temperature 1H NMR spectra provided thermodynamic parameters related to the boat-to-boat interconversion of the cyclohexene ring fused to the fullerene moiety. The mass spectra of the prepared cycloadducts show that the retro-Diels–Alder process takes place easily with elimination of the corresponding diene molecule.

Two alternative methods for the preparation of new pyrimidine Diels–Alder cycloadducts from the readily available 2,4-bis(methylsulfanyl)-5,6-dihydrocyclobuta[d]pyrimidine are presented. In the first method, the in situ generated pyrimidine ortho-quinodimethane reacts with various dienophiles to form the respective cycloadducts bearing two methylthio groups, which can be easily replaced by other functional groups. In the second method, one or both of the methylsulfanyl groups of the starting pyrimidine are replaced first and the resulting functionalized pyrimidines are able to undergo Diels–Alder cyclization with different dienophiles to form pyrimidine cycloadducts. These alternative synthetic strategies provide access to a wide variety of pyrimidine cycloadducts with a different substitution pattern on the pyrimidine ring. Yield data indicate that the electronic nature of the functional groups strongly influence the efficiency of the cycloaddition reaction.

The model reaction of cysteine and diacetyl under winemaking conditions resulted in the identification of over 40 products. Of these, 12 were also identified in wine samples. Several products of the model system contained unexpected structures that do not fit the four-carbon skeletal pattern of diacetyl. Possible synthetic routes to one of these products, trimethylpyrazine, are presented.

2,4-Di-tert-butyl-5,6-dialkylpyrimidines were easily obtained in a one-step reaction from dialkyl ketones and pivalonitrile in the presence of triflic anhydride. pKa values determined show that these compounds can be used as highly sterically non-nucleophilic bases. It was applied to the synthesis of vinyl triflates in which the strong TfOH acid is formed. The results were compared with the obtained using commercially available 2,4,6-tri-tert-butylpyrimidine (TTBP).

The reaction of aliphatic esters with methyl thiocyanate and triflic anhydride affords substituted 4-alkoxy-2,6-bis(methylthio)pyrimidines with minor amounts of substituted S-methyl N-alkanoylthiocarbamates. The structure of the starting ester appears to determine the ratio of final products. Methylthio groups on the pyrimidine ring can be easily converted into methylsulfonyl groups by oxidation. Controlled substitution of one or both methylsulfonyl groups leads to the formation of aminodialkoxy- and trialkoxypyrimidines. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

The current report describes a straightforward and facile route to a class of new tetrahydropyrido[4,3-d]pyrimidine derivatives via the reaction of 1-benzylpiperidin-4-one with an alkyl/aryl cyanide or thiocyanate in the presence of triflic anhydride. The reported conversion of the methylthio derivatives into methoxy and uracil systems via 1 represents further useful chemistry.

The one-pot reaction of 1-tetralone with nitriles in the presence of triflic anhydride affords in good yields 2,4-disubstituted 5,6-dihydrobenzo[h]quinazolines, which oxidation with DDQ leads to the corresponding benzo[h]quinazolines. 2-Tetralone undergoes identical process forming 1,3-disubstituted 5,6-dihydrobenzo[f]quinazolines. However, when the reaction of 2-tetralone is carried out with methylthiocyanate as nitrile, 5-methylthiotetrahydrodibenzo[a,i]phenanthridines are isolated in good yields. Easy transformations of the methylthio group offer possible access to a variety of substituted dibenzo[a,i]phenanthridines.

The reported procedure provides a general approach to the synthesis of 2-substituted 5-methyl-4-(methylthio)oxazoles under mild conditions in good yields. The nature of the cyano group does not significantly affect the yields of the reaction and the product thiomethyl group may be reductively cleaved by Raney nickel (86-93%) or oxidized to a methylsulfonyl group by MCPBA (91-97%). The intermediacy of an α-trifloyl species in this reaction is suggested by spectroscopic evidence.

The one-pot reaction of valerolactone with nitriles in the presence of triflic anhydride affords 2,4-disubstituted pyrano[2,3-d]pyrimidines. Subsequent addition of methyl thiocyanate leads to 2,4-bis(methylthio)pyranopyrimidines which can easily be converted into the corresponding methylsulfonyl derivatives. The reaction of these derivatives with different nucleophiles produces a variety of substituted pyranopyrimidines.

The Diels-Alder reactions of the ortho-quinodimethane (o-QDM) thermally generated from 2,4-diphenylciclobutapyrimidine with the dienophiles diethyl maleate, diethyl fumarate and dimethyl acetylenedicarboxylate have been investigated. The reaction afforded 5,6,7,8-tetrallydroquinazoline and quinazoline derivatives. While diethyl maleate formed a mixture of cis- and trans-adducts, diethyl fumarate gave only the trans-adduct. The reaction with methyl acetylenedicarboxylate formed a mixture of 5,8-dihydroquinazoline and quinazoline derivatives.

The reaction of 1-(methylthio)acetone with different nitriles in the presence of triflic anhydride led to the one-pot formation of 2-substituted 5-methyl-4-methylthio-1,3-oxazoles in good yield. 1,2- and 1,4-Bisozaxolyl-substituted benzenes were obtained when the reaction was carried out using aromatic dinitriles. The methylthio group at the C4 position of the oxazole ring was easily removed with Raney nickel to form 2-substituted 5-methyl-1,3-oxazoles in good yields. 4-Methylsulfonyl derivatives were prepared by the oxidation of the MeS group with m-CPBA. The proposed mechanism for the formation of oxazoles involves an unstable 1-(methylthio)-2-oxopropyl triflate, which was detected from the low-temperature NMR spectra.

The one-pot reaction of 1-benzylpiperidin-4-one with different nitriles in the presence of triflic anhydride affords substituted tetrahydropyrido[4,3-d]pyrimidines. Reaction with methylthiocyanate forms the corresponding methylthio substituted tetrahydropyridopyrimidines which can be easily converted into dimethoxy and dicarbonyl derivatives.

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ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTUse of Optical Rotation and NMR Signal Counting To Identify Common AldosesJohn Almy View Author Information Chemistry Department, California State University, Stanislaus, Turlock, CA 95382Cite this: J. Chem. Educ. 2004, 81, 5, 708Publication Date (Web):May 1, 2004Publication History Received3 August 2009Published online1 May 2004Published inissue 1 May 2004https://pubs.acs.org/doi/10.1021/ed081p708https://doi.org/10.1021/ed081p708research-articleACS PublicationsRequest reuse permissionsArticle Views365Altmetric-Citations2LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Carbohydrates,Group theory,Mathematical methods,Mixtures,Students Get e-Alerts

ADVERTISEMENT RETURN TO ISSUEPREVLab-ExptNEXTNotes on Converting to MicroscaleAntonio Herrera and John Almy View Author Information CSU Stanislaus, Chemistry Department, 801 W. Monte Vista Avenue, Turlock, CA 95382Cite this: J. Chem. Educ. 1998, 75, 1, 83Publication Date (Web):January 1, 1998Publication History Received3 August 2009Published online1 January 1998Published inissue 1 January 1998https://pubs.acs.org/doi/10.1021/ed075p83https://doi.org/10.1021/ed075p83research-articleACS PublicationsRequest reuse permissionsArticle Views171Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Cholesterol,Chromatography,Extraction,Grignard reaction,Transition temperature Get e-Alerts

The microscale 1,3-dipolar cycloaddition reaction of Fullerene-C60 with 10-diazoanthrone leading to the methanofullerene adduct is described. The synthesis of the monoadduct and flash chromatography separation of the formed bisadducts was set up for two three hour laboratory periods.