Comprehensive Overview of Heterocyclic Compounds Synthesis and Reactions

The content discusses the synthesis of furan and pyrrole, along with reactions of furan such as ring opening, addition reactions, Diels-Alder reaction, and electrophilic substitution. Various methods for obtaining furfural, reactions of furan with different reagents, and stability considerations are explored. The post provides valuable insights into the chemistry of heterocyclic compounds, specifically furan and pyrrole, and their significance in different disciplines of chemistry.

• Heterocyclic Compounds
• Furan Synthesis
• Pyrrole Synthesis
• Reactions of Furan
• Organic Chemistry

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1. Heterocyclic Compounds 3rd Year Students Special Chem, Chem-Phys, Geo-chem, Zoo-Chem, Bot-Chem Prof. Ahmed El Kady, Prof. Fatehia Korany, Dr. Adel Abdel Gawad, Dr. Asmaa Mouorad 1

2. Synthesis Of Furan 1. From cyclodehydration of 1, 4-diketones by acidic reagents, e.g., H2SO4, ZnCl2, Ac2O and P2O3 I2 EtOOC COOEt 2CH3COCH2COOEt + 2C2H5ONa CH3COCHCOOEt HC C O HC Na+ CH3 C CH3 O COOEt H2SO4 EtOOCC CC CH3 H3C H3C O C OH H3C OH 2. From knorr-pyrrole synthesis Description: Paal-Knorr furan synthesis mechanism [6] 2

3. Synthesis Of Furan 3. Feist s synthesis H3C H3C C O H3C C OH HC COOEt C CH3 OH CH2Cl CH Cl O CH3 Chloroacetone E.A.A 4. From decarboxylation of furoic acid. + CO2 COOH O O 3

4. Synthesis Of Furan 5. Furfural (furan 2-carboxaldehyde) Furfural is commercially obtained from pentose (occurred in oat hulls) by stream distillation HO OH CHO CHO CHO O OH OH OH OH 6. By treatment of -hydroxyketones and acetylenic compounds CO2CH3 OH R C=O CO2CH3 R CO2CH3 C C K2CO3 H+ R H2C OH -H2O CO2CH3 CO2CH3 CO2CH3 O O 4

5. Synthesis Of Pyrrole 5

6. Reactions Of Furan 1. Ring opening of furan: The mildest acidic conditions required to affect the hydrolysis of furan into succinaldehyde to prevent the polymerization H+ H2O OHC CHO O O H 2. Addition reactions of furuan: a) Reduction: + H2 O O THF 6

7. Reactions Of Furan b) Diels-Alder reaction: O O H C O + O O O C H O O c) Addition of carbenes (with diazomethane): CH2N2 -N2 O O 7

8. Reactions Of Furan d) Furanis not stable in presence of air and usually stabilized by addition of small amount of hydroquinone. Air oxidation takes place by 2, 5 addition forming peroxide. Hydrogenation of furan peroxide gives succinaldehyde. O2 [H] H2C CH2 O O O OHC CHO O 3. Electrophilic substitution of furan: *Furan cannot be directly nitrated with nitric acid (is very readily attack by oxidizing agents). 2-Nitrofuran may be prepared by nitrating furan with acetyl nitrate (CH3COONO2). Similarly, furan cannot be directly sulphonated, but 2-sulphonic acid may be prepared by action of SO3/pyridine on furan. *If (-I) group is present in the ring, then sulphonation can be carried out directly, e.g., furoic acid gives furoic 5-sulphonic acid. *Furan reacts readily with halogen, but the liberated (HX) causes polymerization, because of this halogenated furan prepared by indirect method, e.g., by brominating furoic acid and decarboxylating the product, 5-bromofuroic acid to 2-bromofuran by heating in quinolone in the presence of copper bronze. Aluminum chloride attacks furan ring, and Friedel-Crafts is best carried with SnCl4. 8

9. Reactions Of Furan NH3/Al2O3 450 C N H SO3/pyridine O SO3H furan-2-sulphonic acid RCOCI/SnCl2 O COR 2-acylfuran O CH3COONO2 Furan + O2N O O NO2 0 C NO2 2-nitrofuran 2,5-dinitrofuran H2/Ni H2O/H+ HO(CH2)4OH Tetramethyleneglycol O Tetrahydrofuran Hg(OAC)2 Br2 O O Br HgOAc 2-Bromofuran C4H9Li 1-CO2 2-HCl O COOH O Li HCl/HCN 9 O CHO

10. Synthesis Of Furfural 1. From dehydration of aldopentoses HCl CH2OH-(CHOH)3-CHO CHO O CHO CHO CHO CHO C OH H OH C O C O - H2O C H HO H HC H H C H OH H OH H OH H C CH2OH CH2OH CH2OH CH2OH H - H2O OH H CHO CHO 10

11. Synthesis Of Furfural 2. From Gattermann s reaction: H2O + + HCl/HCN CH=NH2 CHO O O O HCl + H-C N + H2O CH=NH CHO O H-C=NH Cl O O 11

12. Reactions Of Furfural Furfural is chemically very similar to benzaldehyde as the following 1. It undergoes oxidation (KMnO4) to furoic acid. 2. When it was submitted to react with sodium hydroxide it undergoes cannizzaro reaction and gives a mixture from furfuryl alcohol and sodium salt of furoic acid. 3. It under goes benzoin condensation and gives furoin. 4. It reacts with aniline in the presence of acetic acid and gives Schiff s base. NH2 O 2 O + Ph-NHCH=CH-CH C furfural aniline HO Schiff's base Brilliant red NPh 12

13. Reactions Of Furfural 5. It reacts with acetone and yields furfurylidene acetone. O O furfurylidene acetone 6. It reacts with CaO/400 C, it loses carbon monoxide and gives furan by steam decomposition. 7. With ammonia and ammonium chloride gives 3-hydroxypyridine. H OH NH3/NH4Cl C CHO O O H2N 13

14. Reactions Of Furfural H2/CuO CH2OH O furfuryl alcohol H2/Ni O CH2OH O tetrahydrofurfuryl alcohol CHO furfural NaOH + (cannizzaro reaction) O O CH2OH COOH furfuryl alcohol furoic acid KMnO4 O COOH furoic acid 14

15. Reactions Of Furfural AC2O/AcONa (perkin reaction) O CH CH COOH O furylacrylic acid CHO furfural Alc./KCN CH (benzoin condensation) O O furoin O OH OXID O O O O furil NaOH OH O COOH 2 furilic acid 15