Chemistry
Furan
Furan is a heterocyclic organic compound that consists of a five-membered aromatic ring with four carbon atoms and one oxygen atom. It is a colorless, flammable liquid with a boiling point of 31.4°C. Furan is used as a starting material for the synthesis of various chemicals and pharmaceuticals.
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6 Key excerpts on "Furan"
eBook - ePub- Gordon Gribble, J. Joule, Gordon W. Gribble(Authors)
- 2005(Publication Date)
- Elsevier Science(Publisher)
Chapter 1Furans as versatile synthons for target-oriented and diversity-oriented synthesis
Dennis L. Wright [email protected] Department of Chemistry, Dartmouth College, Hanover, NH, USA1.1 INTRODUCTION
Furan, more than any other aromatic heterocycle, has found considerable application as a distinct building block for alicyclic, heterocyclic and acyclic substructures in high complexity targets. Furans are commonly found as synthons in natural product synthesis, medicinal chemistry and diversity-oriented synthesis. The focus of this review article will be on processes that lead to an overall de-aromatization of the Furan with special emphasis placed on the use of Furans in the synthesis of complex targets such as natural products and combinatorial libraries. The review is non-comprehensive and surveys the literature from approximately 1995. Earlier examples of these and related strategies can be found in reviews from Padwa <94PHC36 >, Vogel <90BCB395 > and Wright <01CI17 >. Synthesis and functionalization of Furans are not covered but have been extensively reviewed elsewhere <82AHC167 ; 82AHC237 > .1.2 OVERVIEW OF THE CHEMISTRY OF Furan
One of the main reasons that Furan has become such an integral part of modern synthetic strategies relates to the ready availability of the parent heterocycle and many simple derivatives. Furan 1 is prepared by decarbonylation of 2-furfuraldehyde 2 which arises from acidic hydrolysis of the pentosan derivatives found in cornhusks and other agricultural products. A variety of simple Furan-derived building blocks 1 -10 are offered commercially, some of which are shown below (Figure 1 ).Figure 1However, the primary reason for the versatile role of Furan relates to the ease with which it is transformed to a variety of non-aromatic structures. In many instances, Furan behaves in a manner analogous to other aromatic ring systems, undergoing a full range of electrophilic aromatic substitution reactions, direct metallations and even nucleophilic aromatic substitution. However, it also shows behavior typical of non-aromatic alkenes and dienes, undergoing addition reactions and cycloadditions. In comparison to the sulfur and nitrogen analogs, Furan only benefits from approximately 16 kcal/mol of resonance stabilization energy, making it the least aromatic of the series. From the viewpoint of a synthetic chemist, Furan can be regarded as a highly flexible and versatile four-carbon building block. Many synthetic strategies involving Furan center on exploitation of its aromatic-like reactivity to easily incorporate the heterocycle into a more complex system followed by conversion to a non-aromatic moiety. An overview of the major reaction pathways (Scheme 1
eBook - PDF- Ramesh Chandra, Snigdha Singh, Aarushi Singh(Authors)
- 2020(Publication Date)
- Arcler Press(Publisher)
Molecules of Furan, pyrrole, and thiophene, each of them is consisting of five-membered rings, which is made of four atoms of carbon and one atom of oxygen, one atom of nitrogen, and one atom of sulfur respectively. Pyrrole and pyridine are both nitrogen heterocycles and their molecules which are consisting of atoms of nitrogen along with the atoms of carbon in the rings. The molecules of several biological materials consist in part of pyridine rings and pyrrole rings, and these kinds’ materials produce small amount of pyridine and pyrrole upon strong heating. In the matter of fact, both of these substances were explored in the time period of 1850s in an oily mixture formed with the help heating of bones. In the present interval of time, pyrrole, and pyridine are prepared with the help of the synthetic reactions. The prime commercial interest lies in their transformation to the other substances, mainly dyestuffs and drugs. Pyridine is also used as a waterproofing agent, an alcohol denaturant, as a solvent, a rubber additive, and a dyeing adjunct. Organic Synthesis and Organic Reagents 214 Furan is a heterocycle which is consisting of oxygen and they employed mainly in order to transform to other substance (which is consisting of pyrrole). Furfural is a close chemical relative to Furan. Furfural is obtained with the help of oat hulls and corncobs and is used in the production of intermediates for thiophene, nylon, a sulfur heterocycle, that resembles benzene in its chemical as well as physical properties. It is a common contaminant of the benzene that is attained with the help of natural sources and was first discovered through the course of the purification process of benzene. Similar to the other compounds, it is primarily applied for the conversion to the other substances. Thiophene and Furan were both discovered in the later interval of time of 19 th century.
eBook - ePubPyrolysis of Organic Molecules
Applications to Health and Environmental Issues
- Serban C. Moldoveanu(Author)
- 2009(Publication Date)
- Elsevier Science(Publisher)
Chapter 21 Pyrolysis of Aromatic Heterocyclic Compounds
S.C. Moldoveanu
21.1. Aromatic heterocycles containing oxygen
General aspects
Heterocyclic compounds are organic compounds with a ring structure that contains in the cycle at least one carbon atom and one other element, such as N, O, or S. The most common cycles contain five or six atoms, the stability of these rings being higher than that of three, four, seven, or larger rings. However, many heterocyclic compounds with a different number of atoms larger than five or six are known. Heterocyclic rings are either nonaromatic or aromatic. Most nonaromatic heterocyclic compounds are similar in their chemical properties with acyclic compounds. Examples include cyclic ethers, which are similar to ethers, cyclic secondary amines, which are similar to linear secondary amines, etc. These compounds were discussed in previous chapters. Also other cycles containing heteroatoms such as carbohydrates (in cyclic form), lactones, anhydrides, etc., which do not have an aromatic character, were previously discussed. In the present section, the pyrolysis of oxygen-containing cycles with aromatic character, including compounds related to Furan and pyrylium ion, will be presented. Heterocyclic compounds may contain a single cycle or more cycles, which can be isolated or condensed. Compounds with carbon aromatic cycles condensed with heterocycles are also common. Polycyclic aromatic compounds containing heterocycles are sometimes indicated as hetarenes (PHAs).Furan and Furan-related compounds
Furan is an aromatic compound with the participation of the oxygen lone pair in the π electron system to satisfy Hückel's rule, 4n+2 (n=1) electrons. The compound is stable to heating up to about 550°C (also depending on heating time). Furan pyrolysis was reported in the literature for continuous flow pyrolysis that generated mainly water, methane, ethylene, acetylene, and benzene [1] . In a shock wave experiment in the temperature range 1050–1460K, propyne, carbon monoxide, acetylene, and, indirectly, ketene were identified as main products. At high temperatures, allene, 1,3-butadiene, ethylene, methane, 1,3-butadiyne, and benzene were found as secondary products [2] . Further studies [3] were able to identify ketene directly. At low-pressure pyrolysis, only acetylene, ketene, propyne, and CO were identified as products in the pyrolysis [4]
eBook - PDFFood Safety Chemistry
Toxicant Occurrence, Analysis and Mitigation
- Liangli (Lucy) Yu, Shuo Wang, Bao-Guo Sun, Liangli (Lucy) Yu, Shuo Wang, Bao-Guo Sun(Authors)
- 2014(Publication Date)
- CRC Press(Publisher)
35 Biological and Chemical Activities of Furan Takayuki Shibamoto 3.1 INTRODUCTION It has been known for many years that toxic heterocyclic compounds, such as Furan, 5-hydroxymethylfurfural, and 4(5)-methylimidazole, are formed in Maillard reac-tion systems (Shibamoto, 1983). Accordingly, they are found in large numbers in heat-treated foods and beverages. For example, brewed coffee alone contains over 400 heterocyclic compounds (Flament, 2002). Some of them have been recognized as important flavor chemicals, which give pleasant roasted or toasted flavors to cooked foods. Figure 3.1 shows typical unsubstituted heterocyclic compounds and their physical and sensory properties (Arctander, 1969). Among heterocyclic flavor chemicals shown in this figure, Furan may be the only chemical which has both a characteristic desirable flavor and an unacceptable level of toxicity. 3 CONTENTS 3.1 Introduction .................................................................................................... 35 3.2 Formation Mechanisms of Furan ................................................................... 38 3.2.1 Precursors of Furan Formation ........................................................... 38 3.2.2 Proposed Formation Mechanisms in Foods and Beverages ............... 38 3.2.3 Formation of Furan by Maillard Reaction .......................................... 39 3.2.4 Formation of Furan by UV Irradiation ............................................... 40 3.3 Occurrence of Furan in Foods and Beverages ................................................ 40 3.3.1 Analytical Methods for Quantifying Furan ........................................ 41 3.3.2 Furan Found in Coffee ........................................................................ 42 3.3.3 Furan Found in Baby Foods ............................................................... 42 3.3.4 Furan Found in Miscellaneous Foods and Beverages ........................
eBook - ePubCarbofuran and Wildlife Poisoning
Global Perspectives and Forensic Approaches
- Ngaio Richards(Author)
- 2011(Publication Date)
- Wiley(Publisher)
Chapter 1 An overview of the chemistry, manufacture, environmental fate and detection of carboFuranStephen Donovan,1 Mark Taggart,2 Ngaio Richards3,41 Pennsylvania Department of Health, 110 Pickering Way, Lionville, Pennsylvania 19353, USA2 Environmental Research Institute, University of the Highlands and Islands, Castle Street, Thurso, Caithness, Scotland, KW14 7JD, UK3 Working Dogs for Conservation, 52 Eustis Road, Three Forks, Montana 59752, USA4 Department of Life Sciences, Anglia Ruskin University, East Road, Cambridge CB1 1PT, UK1.1 IntroductionThe aim of this chapter is to provide the reader with a comprehensive understanding of carboFuran as a compound and a familiarity with the technical terms used throughout this book. First, we outline the features which differentiate carboFuran from other compounds and detail its chemical properties. We then summarise its environmental fate, in other words what happens to it once it is in the environment, and conclude with a discussion of the most common methods of analysing and detecting carboFuran in environmental samples.1.2 The chemistry and mode of action of carboFuranCarboFuran is an organic compound (meaning that it is made up of a carbon skeleton), composed of a benzoFuranyl component which is connected to a carbamate group (circled in Figure 1.1 ), i.e., derived from carbamic acid. Its molecular formula is denoted as C12 H15 NO3 and its chemical name is: 2,3-dihydro-2,2-dimethyl-7-benzoFuranyl N -methylcarbamate. CarboFuran is a systemic insecticide, which means that when it is applied it enters into a plant, is transported by the sap, and when insects or other pests feed on other parts of the plant, they become poisoned.Figure 1.1 Chemical structure of carboFuranThe chemical structure of carboFuran is shown in Figure 1.1 . As a group, carbamates can be classified into N-methyl carbamates of phenols (e.g., carboFuran, carbaryl (Figure 1.5
eBook - PDFProgress in Heterocyclic Chemistry
A Critical Review of the 1994 Literature Preceded by Two Chapters on Current Heterocyclic Topics
- H. Suschitzky, E. F. V. Scriven(Authors)
- 2013(Publication Date)
- Pergamon(Publisher)
Chapter 5.3 Five-Membered Ring Systems: Furans and Benzo Derivatives WILLY FRIEDRICHSEN and KARSTEN PAGEL Institute of Organic Chemistry, University of Kiel, Germany 5 3.1 INTRODUCTION The chemistry of Furans was a field of lively research in the last two years. There are several reasons for this activity. It is well known, that the Furan ring- both in its native as well as in its reduced form -occurs in a number of natural products. These compounds can exhibit a remarkable pharmaceutical activity. There were numerous reports of studies in this field (isolation, synthesis) <94SL40, 94SL46, 94TL1247, 94JOC4698, 94TL2517, 92MI53001, 95T21, 94TL9435, 94JCS(P1)1975, 94CC1605 94T3363 94JOC715 94T11315 94MI53003, 94JOC3433 94CL2143, 94UC(B)148, 94JOC3472, 94MI53004, 94JPS1163, 94JOC1598, 94P1325, 94CPB1163, 94MI53005, 94CPB1175, 94P249, 94P213, 94P1469, 94MI53006, 94MI53007, 94MI53008, 94CPB1370, 94P1588, 94P1585, 94P-1371, 94P1499, 94MI53009, 94CPB1216, 94CPB1202, 94P163, 94P1297, 94P1271, 94P1285, 94-P1267, 94P39, 94MI53010, 94P1375, 94P133, 94P1527>, and there is continuing interest in regio-and stereoselective synthesis of Furans. Additionally, Furans can act as building blocks <94S1450> as do benzo[c]fiirans (isobenzoFurans) <94JA9921>. 5 3 2REACTIONS Regioselective metallation of 2-substituted Furans with subsequent reaction of the metallated species provides a route to 2,5-disubstituted Furans <93MI53001, 93IJC(B)566, 94TL5335, 94JCS(P1)-2493>. 2,3,5-Trisubstituted Furans can be prepared similarly. A stereospecific synthesis of 2,3-di-functionalized tetrahydrofiirans via a transmetallation-alkylation process of 2-(tri-butylstannyl)tetra-hydroFurans was reported <94TL4183, 94TL4187>. The addition of 2-lithioFuran to chiral cc-alkoxy-nitrones provides a stereoselective approach to α-epimeric ß-alkoxy-ct-amino acids <94S1450>. * 0 - 2-lithioFuran I + 2-lithioFuran/ Et 2 AICI * Ί R N(0H)Bn C0 2 Me 130
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