A Convenient Method for the Preparation of 3-Substituted Furans

Kotake, Hiroshi; Inomata, Katsuhiko; Aoyama, Shin-ichi; Kinoshita, Hideki

doi:10.1246/cl.1977.73

Cited by 10 publications

(6 citation statements)

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“…It is noteworthy that [1,2]Wittig rearrangement following the 1,4-eliminative ring opening reaction proceeded to give a (E,Z)-2,4-dienyl-1,6-diol 48 in a completely stereoselective manner in the case of d-benzyloxy-substituted vinyloxirane (46, R = BnO), which demonstrated a new entry of the "syn-effect" applied to the further stereoselective transformation.…”

Section: "Syn--effect" In the Pd--catalyzed Eliminationmentioning

confidence: 99%

“…[1][2][3][4][5][6] Intrigued by a unique propensity of 2 to undergo facile elimination of a tosyl (Ts) group at the allylic position, we have also developed an alternative method for the preparation of allylic sulfones using Pd-catalyzed allylic substitution reaction as illustrated in Scheme 2. For example, allylic acetates 4 were readily converted to allylic sulfones 5 upon treatment with sodium p-toluenesulfinate in the presence of a catalytic amount of Pd(0) complex.…”

Section: Introductionmentioning

confidence: 99%

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"Syn-Effect" in the Base-Induced Isomerization of Vinylic Sulfones to Allylic Sulfones and the Related Various Reactions

Inomata

2009

J. Synth. Org. Chem. Jpn.

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: "Syn-effect" has been recognized as a major cause of stabilizing the syn-conformation at the transition state of a number of reactions against the steric hindrance. This account deals with the origin of the "syn-effect" on the basis of the stereochemical outcome in the isomerization of vinylic sulfones leading to the formation of allylic sulfones and in the related various reactions. We proposed that a s p* interaction between the s-orbital(s) of the allylic C-H s-bond(s) (or of the C-H s-bond(s) at the a-position for carbonyl compounds) and the antibonding orbital (p*) of the C=C double bond (or of the C=O double bond for carbonyl compounds) is the most important and essential factor for the "syn-effect", though the contribution of a 6p-electron homoaromaticity and/or of a hydrogen bonding cannot be entirely ruled out. Scheme 2fied (Scheme 3). 13Therefore, we started to prepare stereochemically well-defined vinylic sulfones and study the detailed stereochemistry of the isomerization. Consequently, we have found that (E)-vinylic sulfones preferentially provided sterically unfavorable (Z)-allylic sulfones, whose stereochemical course was explainable by so-called "syn-effect". Herein we will briefly introduce the stereochemical outcome in the isomerization of vinylic sulfones to allylic sulfones and in the related various reactions, and discuss the origin of this effect in detail. Regio--and Stereoselective Preparation of Vinylic SulfonesOur initial study focused on the stereoselective synthesis of (E)-and (Z)-vinylic sulfones 14, since the iodotosylation of 1-alkenes followed by triethylamine-induced dehydroiodination of the resulting 2-iodo-1-tosylalkanes 13 mostly provided a mixture of (E)-and (Z)-isomers of vinylic sulfones 14 as summarized in Scheme 4 and their separation into pure isomers turned out to be difficult. [14][15][16] Gratifyingly, 2-pyrrolidinyl-1-tosylalkanes 15 derived from 13 and an excess amount of pyrrolidine underwent a selective Cope elimination upon treatment of the crude products 15 with mCPBA in dichloromethane in the presence of Na 2 CO 3 to provide stereochemically pure (E)-vinylic sulfones (E)-14 in high yields (Scheme 5). 17 This procedure was much easier than an alternative method via a-phenylselenation of 1-tosylalkanes 16 and was applicable on a large scale.A possible key factor for success in the exclusive formation of (E)-14 may be the formation of 16 in favor of 17 in the transition state where the N-oxy-1-pyrrolidinyl group and the hydrogen should adopt eclipsed conformation, in order to avoid a severe steric congestion developed by an alkyl substituent R and the tosyl group (Ts) in 17 (Figure 2).The intermediary b-pyrrolidinylsulfones 15 were also used to prepare a-alkylated vinylic sulfones through a-alkylation followed by oxidative elimination of the pyrrolidinyl group. 15On the other hand, (Z)-14 were selectively synthesized in high yields by the Pd-catalyzed hydrogenation of (E)-2-iodo-1-tosyl-1-alkenes 18, which were prepared by the regio-and stereoselectiv...

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Section: "Syn--effect" In the Pd--catalyzed Eliminationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

"Syn-Effect" in the Base-Induced Isomerization of Vinylic Sulfones to Allylic Sulfones and the Related Various Reactions

Inomata

2009

J. Synth. Org. Chem. Jpn.

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“…4. [61][62][63][64][65][66][67][68] On the other hand, a number of methods for the preparation of pyrroles, which are five-membered heterocyclic compounds similar to furans, have been exploited, 69,70 because they are fundamental constituents of important substances, such as heme, chlorophyll, vitamin B 12 , and some of them have pharmacological activities themselves.…”

Section: Synthesis Of Bilin Chromophores Of Phytochromesmentioning

confidence: 99%

Studies on the Structure and Function of Phytochromes as Photoreceptors Based on Synthetic Organic Chemistry

Inomata

2008

Bulletin of the Chemical Society of Japan

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“…The chemical shifts of the products agreed with the literature values. 23,24 Nitrosation of N-Benzyl-O-benzoylhydroxylamine (6) 7a in 30% Furan/CDCl3 (vol/vol) at -80 °C. N-Benzyl-Obenzoylhydroxylamine (5 mg, 22 mmol) and pyridine (3.6 mL, 44 mmol) were dissolved in a mixture of furan (150 mL) and CDCl3 (350 mL) in an NMR tube.…”

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confidence: 93%

“…All the spectra had approximately the same appearance. The product distribution: 92% benzyl benzoate (δ 5.41), 3% benzyl nitrate (δ 5.25), 4.5% 2-benzylfuran (δ 4.01), 23 and 0.5% 3-benzylfuran (δ 3.68) 24 did not change with time or temperature. There was no evidence of the intermediacy of O-benzylfuranonium ions (absence of signal at δ ∼6).…”

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The Direct Alkylation of π-Rich, Acid-Sensitive Heterocyclic Compounds via Essentially Free Carbocations¹

Darbeau

White

1997

J. Org. Chem.

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Alkylation of pi-rich heteroaromatics such as pyrroles and furans by the standard Friedel-Crafts approach is impractical because the acid catalysts employed (Brønsted or Lewis) induce polyalkylation, ring opening, and polymerization. The present study describes the facile benzylation of pi-excessive heteroaromatics using the nitrosoamide approach, which generates nitrogen-separated carbocation-counterion ion-pairs as the alkylating agent with no catalyst being required. N-Nitrosoamides are favorable sources of carbocations because of the following variables: mildness of the conditions required to generate cations, high reactivity of the unsolvated carbocations formed, solubility of the precursors in a wide range of solvents, homogeneity of the reactions, wide range of decomposition temperatures possible, straightforward chemistry, and excellent product balance. The majority of the cations that are generated in pyrrole (80%) are intercepted by the solvent, and only 20% are intercepted by the counterion; this result provides support for the intermediacy of nitrogen-separated ion-pairs in deamination. A nucleophilicity scale is presented for reactions of selected nucleophiles with essentially free carbocations.

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A Convenient Method for the Preparation of 3-Substituted Furans

Abstract: It was found that ethyl 4,4-dimethoxy-2-phenylthiobutyrate is an useful reagent for the preparation of 3-substituted furans from alkyl halides. 3-Benzylfuran, 3-geranylfuran (nordendrolasin), and 3-octadecylfuran were prepared by the method in good yields.

Cited by 10 publications

References 1 publication

"Syn-Effect" in the Base-Induced Isomerization of Vinylic Sulfones to Allylic Sulfones and the Related Various Reactions

"Syn-Effect" in the Base-Induced Isomerization of Vinylic Sulfones to Allylic Sulfones and the Related Various Reactions

Studies on the Structure and Function of Phytochromes as Photoreceptors Based on Synthetic Organic Chemistry

The Direct Alkylation of π-Rich, Acid-Sensitive Heterocyclic Compounds via Essentially Free Carbocations¹

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A Convenient Method for the Preparation of 3-Substituted Furans

Abstract: It was found that ethyl 4,4-dimethoxy-2-phenylthiobutyrate is an useful reagent for the preparation of 3-substituted furans from alkyl halides. 3-Benzylfuran, 3-geranylfuran (nordendrolasin), and 3-octadecylfuran were prepared by the method in good yields.

Cited by 10 publications

References 1 publication

"Syn-Effect" in the Base-Induced Isomerization of Vinylic Sulfones to Allylic Sulfones and the Related Various Reactions

"Syn-Effect" in the Base-Induced Isomerization of Vinylic Sulfones to Allylic Sulfones and the Related Various Reactions

Studies on the Structure and Function of Phytochromes as Photoreceptors Based on Synthetic Organic Chemistry

The Direct Alkylation of π-Rich, Acid-Sensitive Heterocyclic Compounds via Essentially Free Carbocations1

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The Direct Alkylation of π-Rich, Acid-Sensitive Heterocyclic Compounds via Essentially Free Carbocations¹