Direct Introduction of a Methyl Group at the C5‐Position of 1,2,4‐Triazines: Convenient Synthesis of 6‐Functionalized 5‐Aryl‐2,2′‐bipyridines

2020 ◽  
Vol 5 (9) ◽  
pp. 2753-2755 ◽  
Author(s):  
Alexey P. Krinochkin ◽  
Dmitry S. Kopchuk ◽  
Igor S. Kovalev ◽  
Sougata Santra ◽  
Grigory V. Zyryanov ◽  
...  
Keyword(s):  
Direct Introduction ◽  
Methyl Group ◽  
Convenient Synthesis

Pterins. VIII. The absolute configuration at C 6 of natural 2-Amino-6-[(1'R,2'S)- 1',2'-dihydroxypropyl]-5,6,7,8-tetrahydropteridin-4(3H)-one (L-erythro-5,6,7,8-tetrahydrobiopterin)

1982 ◽  
Vol 35 (4) ◽  
pp. 785 ◽  
Author(s):  
WLF Armarego ◽  
P Waring ◽  
B Paal
Keyword(s):  
Hydrochloric Acid ◽  
Absolute Configuration ◽  
Side Chain ◽  
Methyl Group ◽  
Convenient Synthesis ◽  
The Absolute

The conformation of the side chain of 5,6,7,8-tetrahydrobiopterint (6) in 0.5 M DCl/D2O is predominantly quasi-equatorial (deduced from 3J (13C4a, 1H6) 1.1 HZ), and is the same as that of the methyl group in 2-methyl-1,2,3,4-tetrahydroquinoxaline and in 2-amino-6-methyl-5,6,7,8-tetrahydropteridin-4(3H)-one in the same solvent. Because (-)-(2S)-2-methyl-1,2,3,4-tetrahydroquinoxaline(4) and (-)-(6S)-2-amino-6-methyl-5,6,7,8-tetrahydropteridin-4(3H)-one (5) have the same conformation and negative c.d. spectra (O 248 nm and 263 nm respectively) as does the natural 5,6,7,8, tetrahydrobiopterin (O minimum at 265 nm) in 0.1 M hydrochloric acid, then the absolute conformations of the tetrahydropyrazine rings and the absolute configurations at the chiral centres C2, C6, and C6 of compounds (4), (5) and (6) respectively are the same. Hence the absolute configuration at C6 in natural 5,6,7,8 tetrahydrobiopterin is R.� A convenient synthesis of biopterin on a gram scale is described.

C-Methylation of Organic Substrates: A Comprehensive Overview. Part I. Methane as a Methylating Agent

2020 ◽  
Vol 17 (7) ◽  
pp. 805-813 ◽  
Author(s):  
Saad Moulay
Keyword(s):  
Organic Compounds ◽  
Literature Survey ◽  
Solid Catalyst ◽  
Organic Substrates ◽  
Acid Base ◽  
Direct Introduction ◽  
Comprehensive Overview ◽  
Methyl Group

A literature survey on C-methylation of organic substrates with methane as a methylating agent is analyzed. Of the substrates that undergo C-methylation are benzene, naphthalenes, toluene, alkanes, alkenes, acetonitrile, and other functionalized organic compounds. None of these methylation reactions occur in the absence of a catalyst. A direct introduction of a methyl group on the carbon sites of a molecule is concomitant with the formation of other products, as a result of either a possible rearrangement or a further reaction with methane. Mechanistically, the C-methylation with methane proceeds oxidatively. The products selectivities depend on several factors, mainly on the acid/ base character of the solid catalyst.

Convenient Synthesis of More Complex 2-Substituted 4(3H)-Quinazolinones via Lithiation of 2-Alkyl-4(3H)-quinazolinones

1999 ◽  
Vol 64 (3) ◽  
pp. 515-526 ◽  
Author(s):  
Keith Smith ◽  
Gamal A. El-Hiti ◽  
Mohamed F. Abdel-Megeed ◽  
Mohamed A. Abdo
Keyword(s):  
Addition Product ◽  
Phenyl Isocyanate ◽  
Lithium Diisopropylamide ◽  
Methyl Group ◽  
Convenient Synthesis

2-Methylquinazolin-4(3H)-one has been doubly lithiated, at nitrogen and in the 2-methyl group, with n-butylithium. The lithium reagent thus obtained reacts with a variety of electrophiles (iodomethane, D2O, phenyl isocyanate, benzaldehyde, benzophenone, cyclopentanone, 2-butanone, carvone) to give the corresponding 2-substituted derivatives in very good yields. Reaction of the dilithio reagent with acetonitrile gives an α,β-unsaturated imine by tautomerization of the initial addition product. Double lithiation of 2-ethyl- and 2-propyl-4(3H)-quinazolinones can be achieved using lithium diisopropylamide and the lithiated reagents thus obtained react with similar electrophiles to give the corresponding products in very good yields. In the reaction of the dianion of the 2-ethyl-4(3H)-quinazolinone with iodine, an oxidatively dimerised product was obtained. Lithiation of 2-unsubstituted 4(3H)-quinazolinone does not take place on C-2 under similar conditions.

Use of [13C-methyl]Tropinone to follow the fate of the methyl group during calystegine formation in root cultures of Solanum dulcamara (Solanaceae)

Planta Medica ◽  
2008 ◽  
Vol 74 (09) ◽  
Author(s):  
TA Bartholomeusz ◽  
R Molinié ◽  
A Roscher ◽  
AC Freydank ◽  
B Dräger ◽  
...  
Keyword(s):  
Root Cultures ◽  
Solanum Dulcamara ◽  
Methyl Group

STEROIDSTRUKTUR UND LEBERTOXIZITÄT

1967 ◽  
Vol 54 (1) ◽  
pp. 73-84 ◽  
Author(s):  
H. L. Krüskemper ◽  
G. Noell
Keyword(s):  
Alkaline Phosphatase ◽  
Liver Function ◽  
Blood Coagulation ◽  
Electrophoretic Pattern ◽  
Coagulation Factors ◽  
Blood Coagulation Factors ◽  
Methyl Group ◽  
Liver Functions ◽  
Male Subjects ◽  
Androstane Derivatives

ABSTRACT In male subjects investigations have been carried out regarding the effect of C1- and C17-methylated androstane derivatives (20 mg per day, orally, two weeks) on liver functions (parameters: activities of GPT, GOT, alkaline phosphatase and cholinesterase in serum; electrophoretic pattern; blood coagulation factors V, VII, X and prothrombin; BSP-retention). In addition to the well known hepatotropic action of 17α-alkylated C-19-steroids a quasi-axial 1α-methyl configuration (in 1α-methylandrost-2-en-17β-ol) definitely increased BSP-retention and several coagulation factors. These steroid effects decreased gradually when a methyl group was introduced in C1 equatorially (1-methylandrost-1-en-17β-ol-3-one) or quasi-equatorially (1β-methylandrost-2-en-17β-ol), the latter compound completely lacking from any influence on parameters of liver function under investigation.

A Reinvestigation of the Deceptively Simple Reaction of Toluene with ●OH, and the Fate of the Benzyl Radical. I. a Combined Thermodynamic and Kinetic Study on the Competition Between ●OH Addition and Hydrogen Abstraction Reactions.

2019 ◽  
Author(s):  
Zoi Salta ◽  
Agnie M. Kosmas ◽  
Marc E. Segovia ◽  
Martina Kieninger ◽  
Oscar Ventura ◽  
...  
Keyword(s):  
Density Functional ◽  
Room Temperature ◽  
Hydrogen Abstraction ◽  
Reaction Rates ◽  
Composite Model ◽  
Alternative Mechanism ◽  
Radical Intermediate ◽  
Experimental Conditions ◽  
Methyl Group ◽  
Benzyl Radical

This work reports density functional and composite model chemistry calculations performed on the reactions of toluene with the hydroxyl radical. Both experimentally observed H-abstraction from the methyl group and possible additions to the phenyl ring were investigated. Reaction enthalpies and heights of the barriers suggest that H-abstraction is more favorable than ●OH addition to the ring. The calculated reaction rates at room temperature and the radical-intermediate product fractions support this view. This is somehow contradictory with the fact that, under most experimental conditions, cresols are observed in a larger concentration than benzaldehyde. Since the accepted mechanism for benzaldehyde formation involves H-abstraction, a contradiction arises that begs for an explanation. In this first part of our work we give the evidences that support the preference of hydrogen abstraction over ●OH addition and suggest an alternative mechanism which shows that cresols can actually arise also from the former reaction and not only from the latter.

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