Furan Derivatives

4 Key excerpts on "Furan Derivatives"

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  eBook - ePub

  Furfural

  An Entry Point of Lignocellulose in Biorefineries to Produce Renewable Chemicals, Polymers, and Biofuels

  • Manuel López Granados, David Martín Alonso(Authors)
  • 2018(Publication Date)
  • WSPC (EUROPE)

    (Publisher)

  3 ]).

  The principal physical properties of furfural and its main derivatives are shown in Table 1.1 [3 ]. The applications of products derived from furfural are multiple, Table 1.2 showing some of their main applications, as well as their synthetic route based on furfural. Further details will be given in Chapter 3 .

  Due to the two chemical functionalities present — aldehyde group and aromatic ring — furfural can undergo typical aldehyde reactions, such as nucleophilic additions, condensation reactions, oxidations or reductions, as well as others associated to the furan ring such as electrophilic aromatic substitution or hydrogenation.

  The purpose of this chapter is to give an overview of furfural chemical reactivity based on the organic chemistry fundamentals, intending to help the reader to understand the multiple possible reactions that furfural has in function of the different functionalities of the molecule: the aromatic ring and the carbonyl group.

  1.2.Furan and Furan Derivatives

  1.2.1.Furan structure, physical properties and synthesis

  Furan is a heterocyclic organic compound consisting of a fivemembered aromatic ring with four carbon atoms and an oxygen atom. It is a colorless, highly volatile and flammable liquid with a low-temperature boiling point (Table 1.1 ). It is slightly soluble in water but readily soluble in common organic solvents such as alcohol, ether or acetone.

  Table 1.2.Applications and synthetic procedure of the main furfural derivatives (adapted from Ref. [3

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  Progress in Heterocyclic Chemistry

  • Gordon Gribble, J. Joule, Gordon W. Gribble(Authors)
  • 2005(Publication Date)
  • Elsevier Science

    (Publisher)

  Chapter 1

  Furans as versatile synthons for target-oriented and diversity-oriented synthesis

  Dennis L. Wright [email protected]     Department of Chemistry, Dartmouth College, Hanover, NH, USA

  1.1 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 1

  However, 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

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  Progress 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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  Science of Synthesis: Knowledge Updates 2018 Vol. 3

  • Mark Bagley, Klaus Banert, John A. Joule, Toshiaki Murai, Christopher A. Ramsden, Mark Bagley, Klaus Banert, John A. Joule, Toshiaki Murai, Christopher A. Ramsden(Authors)
  • 2018(Publication Date)
  • Thieme Chemistry

    (Publisher)

  1 10.2 Product Class 2: Benzo[c]furan and Its Derivatives H. Kwiecien ´ 10.2.1 Product Subclass 1: Benzo[c]furans The structure and numbering of the parent member of this product class, systematically named benzo[c]furan, are presented in Scheme 1. The ring system has also been named (with the same atom numbering) as isobenzofuran and 2-benzofuran. Chemical Abstracts uses the isobenzofuran name for 1; however, the systematic name is used as well. In the earlier literature, the skeleton was called 2-benzofurane. Scheme 1 Structure and Ring Numbering of Benzo[c]furan O 1 2 3 3a 4 5 6 7 7a 1 There are no known naturally occurring compounds of the fully unsaturated ring system. The first synthesis of a stable benzo[c]furan, 1,3-diphenylbenzo[c]furan (2) (Scheme 2), was reported in 1906. [1] The unstable parent compound 1 has been known since 1964, when its existence as a transient intermediate was first established by trapping it with a reac- tive dienophile and isolation as the Diels–Alder adduct. [2,3] In later work (1971), the elusive pure benzo[c]furan (1) was isolated and characterized. [4,5] Since that time, a wide variety of benzo[c]furan-related analogues substituted at the furan and/or benzene rings, as well as various annulated homologues of the parent compound, have been prepared. These ben- zo[c]furans are valuable substrates or intermediates for the synthesis of more complex molecules, which can be useful products for technical and biomedical applications. Some representative examples of such benzo[c]furans are given below. The parent benzo[c]furan (1), a very reactive molecule, can be used as a precursor monomer for the preparation of polymeric thin films. The optical properties and sur- face-dependent growth characteristics of the poly(benzo[c]furan) obtained by chemical vapor deposition techniques can provide potential optical (such as components of optical waveguides) and microfluidic applications.

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