Heterocyclic mesomeric betaines

Publisher Summary The chapter focuses tautomerism and electronic Structure of biological pyrimidines. The understanding of the tautomeric properties of the purine and pyrimidine bases of the nucleic acids and the determination of the electronic properties of the principal tautomers are of fundamental importance in molecular biology, in particular, in connection with the theory of mutations. The principal tautomeric properties of the fundamental biological pyrimidines-cytosine, uracil, and thymine-are due to the presence in these N-heteroaromatic compounds of electron-donor substituents, such as NH and OH, and of SH in some important analogs. The chapter discusses tautomerism of cytosine and presents the essential physicochemical properties of cytosine and some of its derivatives and to the theoretical interpretation of these properties. The chapter also discusses tautomerism and physicochemical properties of uracil and thymines and to give a theoretical interpretation of these properties. The study of the optical properties of naturally occurring pyrimidines and purines is a problem of great interest in molecular biology. The knowledge of these properties provide information important for understanding energy transfer, hypochromism, photochemistry, optical rotatory dispersion, circular dichroism, magnetic optical rotator dispersion, and magnetic circular dichroism of DNA, RNA, and related model systems. Tautomerism, electronic structures, and spectra of rare pyrimidine bases of the nucleic acids have also been discussed.

Taulomerism and Electronic Structure of Biological Pyrimidines

Publisher Summary The chapter focuses on the recent advances in the chemistry of benzo[b]furan and its derivatives. The chemistry of benzofuran derivatives has developed in a spectacular fashion: research in this field has reached such a scale that the period covered by this review has given rise to a larger number of papers than that between 1870 and 1950. It has proceeded along the following three main lines: (1) Extraction, determination of structures, partial or total synthesis of the simple or complex heterocyclic derivatives constituting the natural benzofuran derivatives of vegetable origin. (2) Synthesis of benzofuran derivatives with physiological, pharmacological, therapeutic, or toxic properties. (3) Studies on the reactivity of benzofuran and its derivatives from the chemical and physical point of view. Many substances with physiological, pharmacological, therapeutic, or toxic properties are to be found among natural products with a benzofuran ring. As to synthetic benzofuran derivatives prepared for the study of their physiological properties, their number is large. Benzofuran is prepared in semicommercial amounts. The chapter discusses the presence of benzofurans in coal tar and in petroleum. Natural benzofuran derivatives have also been discussed. The numerous syntheses of the benzofuran ring may be classified under four headings: (1) Formation of the heterocyclic ring from an aromatic substrate (2) formation of the heterocyclic ring from a nonaromatic substrate (3) fusion of the benzene ring to a furan substrate (4) formation of the heterocyclic ring from other heterocyclic compounds.

Recent Advances in the Chemistry of Benzo[b]furan and Its Derivatives. Part I: Occurrence and Synthesis

The 3,4-dioxygenated 5-hydroxy-4-aryl-quinolin-2(1H)-one alkaloids. Results of 20 years of research, uncovering a new family of natural products

3-Substituted 4-hydroxy-2(1H)-quinolones3,5,7 are halogenated with bromine or sulfuryl chloride to yield the quinolinediones9 or10. Reaction of3,5,7 with chloroform gives the dichloromethyl quinolinediones11. Halogen exchange leads from the chloro quinolinediones10 to fluoro quinolinedones12 and to azido quinolinediones13. Similarly the dichloro quinolinedione10 an reacts to the difluoro quinolinedione14, which is reduced to the 3-fluoro-4-hydroxyquinolone16 and reacts again with sulfuryl chloride to give the mixed 3-chloro-3-fluoroquinolinedione15.

Halogenation reactions in position 3 of quinoline-2,4-dione systems by electrophilic substitution and halogen exchange

Durch Alkylierung der 4-Hydroxy-2-chinolone 1 und 7 mit Allylbromid entstehen die Verbindungen 2,3,4,5 und 8. Die Substanzen 3,4 und 8 werden sowohl durch direkte C-Alkylierung als auch durch Claisen-Umlagerung der entsprechenden Allylather gebildet. - Das 3-Allylderivat 3 cyclisiert in HBr/AcOH zum linearen Furochinolon 9, welches sich beim Erhitzen in das angulare Derivat 11 umlagert, das auch durch Thermolyse von 3 zuganglich ist. 11 und 9 lassen sich oberhalb 200°C an Pd/C zu 12 dehydrieren Die Tetrahydrochinolindione 4 und 8 reagieren in HBr/AcOH zu 15 bzw 17 Durch katalytische Hydrierung von 4 an Pd entstehen 14 und 16; aus 8 entsteht hierbei 18 In Gegenwart von Na-Acetat erfolgt jedoch zum Teil unter Hydrogenolyse der CC-Bindung in 4 und 8 die Bildung von 6 bzw. 7.



Alkylation of Ambident Heterocyclic Anions, V. Rearrangement Reactions of Heterocyclic Compounds, III. The Allylation of 4-Hydroxy-2-quinolone



Alkylation of the 4-hydroxy-2-quinolones 1 and 7 with allyl bromide yields 2, 3, 4, 5, and 8. Compounds 3, 4, and 8 are formed both by direct C-alkylation and by Claisen-rearrangement of the corresponding allyl ethers. — The 3-allyl derivative 3 undergoes cyclisation in HBr/AcOH to give the linear furoquinolone 9, which is rearranged at higher temperature to the angular derivative 11. Compound 11 is also obtained by thermolysis of 3. Dehydrogenation of 11 or 9 on Pd/C above 200°C yields 12. The tetrahydroquinolindiones 4 and 8 react in HBr/ AcOH to give 15 and 17, resp. The catalytic hydrogenation of 4 on a Pd-catalyst produces 14 and 16; in the same way 18 is obtained from 8. However, in the presence of sodium acetate partial hydrogenolysis of the CC bond in compounds 4 and 8 occurs, leading to the formation of 6 and 7.

Alkylierung ambidenter Heterocyclen-Anionen, V. Umlagerung von Heterocyclen, III. Zur Allylierung des 4-Hydroxy-2-chinolons

Die Alkylierung der “Malonyl-α-aminopyridine”1a und1b mit Benzylbromid inDMF liefert neben den N-alkylierten Betainen2a bzw.2b als Hauptprodukte die Ather3a bzw.3b. Bei der Alkylierung in Methanol verschiebt sich dieses Verhaltnis zugunsten der Betaine. Die Benzylierung in wasr. NaOH gibt neben den genannten Verbindungen vorwiegend solche, die Folgeprodukte einer primaren C-Alkylierung sind (6a, 6b und7).

Alkylierung ambidenter Heterocyclen-Anionen, 4. Mitt.: Zur Alkylierung von “Malonyl-α-aminopyridinen”

Die Reaktion der Chinisatin-aminale1, 2 und10 mit Phenol in Eisessig/H2SO4 gibt die Carbinole5, 6 und12, die mit Zn/HCl zu den entsprechenden 4-Hydroxy-3-p-hydroxyphenyl-carbostyrilen7, 8 und13 reduziert werden. Die Kondensation des Chinisatin-hydrats (3) mit Malonester zu15 last sich mit Morpholin katalysieren; die Reaktion von3 mit 2-Picolin zu17 erfolgt beim Erhitzen der Komponenten.

Peter F. Fritz

Papers

Alkylierung ambidenter Heterocyclen-Anionen, V. Umlagerung von Heterocyclen, III. Zur Allylierung des 4-Hydroxy-2-chinolons

Alkylierung ambidenter Heterocyclen-Anionen, 4. Mitt.: Zur Alkylierung von “Malonyl-α-aminopyridinen”

Synthesen von Heterocyclen, 131. Mitt.: Über die Reaktionen einiger Mesoxalylheterocyclen und ihrer Aminale

Alkylierung ambidenter heterocyclen-anionen 5. mitt. umlagerung von heterocyclen 3. mitt. allylierung des 4-hydroxy-2-chinolons

Alkylierung ambidenter heterocyclen-anionen 4. mitt. alkylierung von ′malonyl-alpha-aminopyridinen′