Cyclization of Ph2Si(NHNHMe)2. II. Reactions with methyl iodide, HCl, and Ph2SiCl2, and thermolysis

1994 ◽  
Vol 72 (8) ◽  
pp. 1759-1763 ◽  
Author(s):  
Jiliang He ◽  
John F. Harrod
Keyword(s):  
Methyl Iodide ◽  
Membered Ring ◽  
Cyclization Reactions

The reaction of Ph2Si(NHNHMe)2 (1) with MeI results in a mixture of two six-membered ring isomers, 1,2,4,5-tetraaza-1,4-dimethyl-3,3,6,6-tetraphenyl-3,6-disilacyclohexane (2), 45%, and 1,2,4,5-tetraaza-1,5-dimethyl-3,3,6,6-tetraphenyl-3,6-disilacyclohexane (3), 40%. The reaction of 1 with HCl or Ph2SiCl2 proceeds in a similar fashion. The thermolysis of 1 is studied from 25–600 °C. In the range of 250–300 °C, about 50% of 1 is converted into 2,3, and 1,2,4-triaza-1-methyl-4-methylamino-3,3,5,5-tetraphenyl-3,5-disilacyclopentane, 8. Possible pathways for the formation of 2,3, and 8 in these cyclization reactions are discussed.

Monosaccharide permethylation products for gas chromatography - mass spectrometry: how reaction conditions can influence isomeric ratios

1997 ◽  
Vol 75 (10) ◽  
pp. 1385-1392 ◽  
Author(s):  
Daniel Derbie Asres ◽  
Hélène Perreault
Keyword(s):  
Mass Spectrometry ◽  
Methyl Iodide ◽  
Reaction Times ◽  
Membered Ring ◽  
Gas Chromatography Mass Spectrometry ◽  
Reaction Parameters ◽  
Methylation Analysis ◽  
Reaction Conditions ◽  
Starting Point

Methylation analysis has been widely used for determination of carbohydrate structures by mass spectrometry. Permethylation of monosaccharides yields mixtures of anomeric pyranosides and furanosides. This paper discusses the influence of some of the permethylation reaction parameters on the proportions of isomeric products obtained. The ratios of three five- and six-membered ring products obtained from two permethylated monosaccharides, D-galactose and L-fucose, have been determined as a function of reaction parameters. The method of Ciucanu and Kerek (1) (methyl iodide in dimethyl sulfoxide (DMSO) in the presence of sodium hydroxide (NaOH)) was used as a starting point. The "conventional" method consists of mixing all of the reagents with the substrate and allowing the reaction to proceed with stirring. Both D-galactose and L-fucose under these conditions produced two main permethylated isomers, a furanoside and a pyranoside, along with two other minor isomeric components. We have investigated the effect on the proportion of products obtained of mixing DMSO, substrate, and NaOH for various times prior to the addition of methyl iodide. Results for D-galactose showed that shorter times enhanced the formation of permethylated furanoside isomers, while reducing the proportion of pyranosides. In other sets of experiments, the time and temperature of reaction, following the addition of methyl iodide, were studied. The indication is that 15 min are sufficient to produce complete methylation, with longer reaction times yielding the same results. Again for D-galactose, low reaction temperatures (ca. 10 °C) favored formation of furanoside products. Higher temperatures yielded higher pyranoside/furanoside ratios. Higher quantities of NaOH also favored formation of the main galactopyranoside product. As for L-fucose, the ratio of the main furanoside vs. pyranoside products obtained by permethylation varied in a way similar to permethylated galactoside. Thus, higher temperatures and longer reaction times favored the main fucopyranoside product. Gentler conditions (i.e., shorter reaction times and lower temperatures) significantly favored the formation of the main fucofuranoside product. These results are interesting as they show the possibility of controlling the relative abundance of permethylated isomers of fucose and galactose. They also constitute a warning to chemists who use methylation procedures in their analyses, to the effect that permethylation products may vary considerably if the reaction conditions are not carefully controlled. Keywords: glucose, galactose, fucose, TLC, GC–MS, permethylation, monosaccharides.

Sulfonamide Analogues of Creatinine. The Synthesis of 3-Amino-4,5-dihydro-1,2,4-thiadiazole 1,1-Dioxides from Base-Induced Cyclization Reactions

1997 ◽  
Vol 50 (10) ◽  
pp. 1027 ◽  
Author(s):  
Fares A. Fares ◽  
Damon D. Ridley ◽  
Ping Yin
Keyword(s):  
Methyl Iodide ◽  
Cyclization Reactions ◽  
Methyl Derivative

We report the preparation of 3-amino-4,5-dihydro-1,2,4-thiadiazole 1,1-dioxide and of its 4-methyl derivative which are of interest as potential analogues of creatinine. The thiadiazoles are obtained from chloromethylsulfonylation ofS-benzylisothiourea, followed by cyclization of the chloromethanesulfonamide under basic conditions in the presence of 2-(t-butoxycarbonyloxyimino)-2-phenylacetonitrile or of methyl iodide.

Extended Dötz-Like Cyclization Reactions Towards the Synthesis of Eight-Membered Ring-Containing Polycycles: Scope and Theoretical Studies

2007 ◽  
Vol 13 (27) ◽  
pp. 7682-7700 ◽  
Author(s):  
José Barluenga ◽  
Martín Fañanás-Mastral ◽  
M. Angel Palomero ◽  
Fernando Aznar ◽  
Carlos Valdés
Keyword(s):  
Membered Ring ◽  
Theoretical Studies ◽  
Cyclization Reactions

scholarly journals Cascade cyclization reactions of alkylidenecyclopropanes for the construction of polycyclic lactams and lactones by visible light photoredox catalysis

2020 ◽  
Vol 7 (2) ◽  
pp. 374-379 ◽  
Author(s):  
Mintao Chen ◽  
Yin Wei ◽  
Min Shi
Keyword(s):  
Visible Light ◽  
Membered Ring ◽  
Visible Light Photocatalysis ◽  
Photoredox Catalysis ◽  
Cyclization Reactions ◽  
Cascade Cyclization

A facile method for the synthesis of seven- and eight-membered ring-containing polycyclic lactams and lactones by visible light photocatalysis has been developed.

Construction of Versatile N-Heterocycles from in situ Generated 1,2-Diaza-1,3-dienes

2019 ◽  
Vol 23 (2) ◽  
pp. 164-187 ◽  
Author(s):  
Zhangpei Chen ◽  
Lingxin Meng ◽  
Zhiqiang Ding ◽  
Jianshe Hu
Keyword(s):  
Natural Products ◽  
Heterocyclic Compounds ◽  
Materials Science ◽  
Membered Ring ◽  
Research Interest ◽  
Cyclization Reactions ◽  
Bioactive Natural Products ◽  
Synthetic Drugs ◽  
Nitrogen Containing Compounds

N-Heterocyclic architectures are omnipresent in many bioactive natural products, synthetic drugs, and materials science, thus have evoked a vast research interest of academic, as well as industrial chemists. Recently, several efficient methods have been developed for the preparation of various nitrogen-containing compounds with in situ generated 1,2-diaza-1,3-dienes from the easily available precursors including α -haloketohydrazones, α-hydroxyl ketohydrazones, thiadiazole dioxides or their analogues, and other simple hydrazones. These methods are considered powerful tools in the synthesis of five-, six- and seven-membered ring heterocyclic compounds with good to excellent levels of conversions and selectivities. This review mainly summarizes recent advances on the chemistry of construction of versatile N-heterocycles from in situ generated 1,2-diaza-1,3- dienes and presents an extensive summary of the application scopes and limitations of the corresponding cyclization reactions. Moreover, enantioselective approaches are also covered.

Radical-Initiated Hydrosilylation-Cyclization Reactions of Bis(vinyldimethylsilyl) Compounds, CH2=CH(CH3)2SiXSi(CH3)2CH=CH2 (X = O, CH2, NH, NCH3, NSi(CH3)3

1994 ◽  
Vol 49 (12) ◽  
pp. 1818-1826 ◽  
Author(s):  
Dietmar Seyferth ◽  
Holger Friedrich ◽  
Shane W. Krska
Keyword(s):  
Membered Ring ◽  
Trans Isomers ◽  
Cyclization Reactions ◽  
Tert Butyl ◽  
Cis And Trans Isomers ◽  
Butyl Peroxide ◽  
Cis And Trans

The di-tert-butyl peroxide-initiated reactions of triethyl- and tri-n-propylsilane with bis-(vinyldim ethylsilyl) compounds, CH2=CH(CH3)2SiXSi(CH3)2CH=CH2(X-O,CH2, NH,NCH3 and NSiMe3) resulted in hydrosilylation-cyclization to give mixtures of trialkylsilylm ethyl-substituted disilacyclohexanes and trialkylsilylm ethyl-substituted disilacyclopentanes. The ratio of six-membered to five-membered ring products obtained is dependent on the linking group X and decreased in the order X=O>CH2>NH>NCH3. For X = NSiMe3 only a mixture of the cis and trans isomers of the five-membered ring product was obtained.

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