Alkamine Esters of Fluorenonecarboxylic Acids<sup>1</sup>

Ray, Francis Earl; Rieveschl, George

doi:10.1021/ja01245a022

Cited by 15 publications

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“…The oxidation of 6 yielded 3,3-di(2-fluorenoyl)-2-butanone, di(2fluorenoyl) ketone,20 and fluorenone-2-carboxylic acid. 21 Consequently, the pinacolone 6 is established as the compound formed by the migration of the 2-fluorenyl group in 5; the isomer due to methyl group migration is shown to be absent in these experiments. The hydrogenation of 6 afforded 7, which gave, of course, 9a and 9b by reaction with hydriodic acid.…”

Section: Scheme IV Chjmentioning

confidence: 83%

Clemmensen reduction of 2-acetylfluorene. Pathways for the formation of 2,3-di(2-fluorenyl)butane and its homologues

Minabe¹,

Yoshida²,

Fujimoto³

et al. 1976

J. Org. Chem.

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The Clemmensen reduction of 2-acetylfluorene gave not only 2-ethylfluorene but also 2-(a-hydroxyethyl)fluorene, 2-vinylfluorene, cis-and trans-2,3-di(2-fluorenyl)-2-butene, meso-and dl-2,3-di(2-fluorenyl)butane, 2,3-di(2.fluorenyl)-2,3-butanediol, 3,3-di(2-fluorenyl)-2-butanone, and 3,3-di(2-fluorenyl)-2-butanol. The confirmation of these compounds was achieved by established syntheses. The Clemmensen reduction of 2-acetylfluorene may proceed through the corresponding carbinol, 2-(a-hydroxyethyl)fluorene, to the normal reduction product, 2-ethylfluorene.The Clemmensen reduction of 2-acetylfluorene ( 1)112 has been reported by Campbell and Wang3 to yield only 2-ethylfluorene (2)4-6 in 45% yield.The present paper deals with the reinvestigation of this reduction and 1 was found to form not only 2 (76%) but also intermediary compounds, 2-(a-hydroxyethyl)fluorene (3)7 and 2-vinylfluorene (4),6-8 and the related dimeric products, namely 2,3-di(2-fluorenyl)-2,3-butanediol ( 5 ) , 3,3-di(2-fluoreny1)-2-butanane (6), 3,3-di(2-fluorenyl)-Z-butanol (7), cis-(Sa) and trans-2,3-di(2-fluorenyl)-2-butene (Sb), and meso-(9a) and dl-2,3-di(2-fluorenyl)butane (9b). The structural proof for these compounds was confirmed by authorized syntheses.Scheme I 1 2 3 4 5 8 0These results suggest, on the grounds of the formation of intermediaries 3 and 4, t h a t the reduction sequence of 1 may differ somewhat from the conventional concept of the Clemmensen r e d u c t i~n ;~ generally, the reaction cannot proceed through the corresponding carbinol since the carbinol itself is not reduced.The reduction of 1 gave, in addition to 2, a pair of cis, trans isomers, Sa and Sb, and diastereomers of 9a and 9b. The formation of these isomers provides some interesting stereochemical information, because the recent studies of the Clemmensen reduction have rarely observed such abnormal products as these stereoisomers. Sequence of the Formation of 2-Ethylfluorene (2) by the Clemmensen Reduction of 2-Acetylfluorene (1).The reduction of 1 and its homologues was carried out in xylene using amalgamated zinc and hydrochloric acid according to t h e method described in Organic reaction^.^ These results are summarized in Table I.At an initial stage of the reduction, 1 yielded 2,3,4,5,6,9a, and 9b. Carbinol 3 was also reduced to 2 accompanied by small amounts of 9a and 9b as easily as in the case of 1. The Clemmensen reduction of olefin 4 afforded 2, but the yield of 2 was smaller than t h a t from 1. Additionally, the deuteriocarbinol, 2-(a-hydroxyethyl)fluorene-C,,0-dz, was converted into 2-ethylfluorene-C,-d and meso-and dl-2,3-di(2-fluorenyl)butane-Cz,C3-d~ under similar reaction conditions, as Scheme I1 shows. Scheme I1@&-=FI -These findings are explained by assuming that the carbinol 3 is one of the important intermediates in the Clemmensen reduction of 1. T h e sequence of the formation of 2,3,4, and 9 is presumed as Scheme 111. Carbinol 3 may be formed from Scheme I11 , OH . Fl-C;CH3___) iF1-A-CI13

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Section: Scheme IV Chjmentioning

confidence: 83%

Clemmensen reduction of 2-acetylfluorene. Pathways for the formation of 2,3-di(2-fluorenyl)butane and its homologues

Minabe¹,

Yoshida²,

Fujimoto³

et al. 1976

J. Org. Chem.

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“…Compound 1 was obtained by the solvothermal reaction of Zn(OAC) 2 with H 2 FDC in DMSO and ethanol, and it was characterized by single-crystal X-ray analyses . The compound is formulated as [Zn(DMSO) 6 ] 1/6 [(Zn 4 O)(FDC) 3 (DMSO) 3/2 (OH) 1/3 (H 2 O) 1/6 ][(Zn 4 O)(FDC) 3 (DMSO) 2 ]·15DMSO·17H 2 O .…”

mentioning

confidence: 99%

Metal−Organic Framework Based on [Zn₄O(COO)₆] Clusters: Rare 3D Kagomé Topology and Luminescence

Sun

Cheng

et al. 2009

Crystal Growth & Design

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“…Fluorenone derivatives are known to display a variety of biological activities. [1][2][3] Also, several methoxy and hydroxyfluorenone derivatives are natural products whose syntheses have recently been described. [4][5][6][7][8][9] As part of our investigation into the protein kinase inhibitory activity of substituted fluorenones, 10 we desired a convenient method for preparing all possible dihydroxy regioisomers in which substitution occurs on only one aromatic ring of the fluorenone nucleus.…”

mentioning

confidence: 99%

An Efficient Synthesis of Dihydroxyfluorenones via in Situ Pd(0)-Catalyzed Cross-Coupling

Ciske¹,

Jones²

1998

Synthesis

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All six dimethoxyfluorenones 6a-f and dihydroxyfluorenones 7a-f , wherein substitution occurs at only one aromatic ring, were conveniently prepared by palladium(0)-catalyzed cross-coupling reactions of aryl bromides/triflates 2a-e with in situ generated arylboranes, derived from o -bromobenzamide 1a and o -bromophenyloxazoline 1b .Fluorenone derivatives are known to display a variety of biological activities. 1-3 Also, several methoxy and hydroxyfluorenone derivatives are natural products whose syntheses have recently been described. [4][5][6][7][8][9] As part of our investigation into the protein kinase inhibitory activity of substituted fluorenones, 10 we desired a convenient method for preparing all possible dihydroxy regioisomers in which substitution occurs on only one aromatic ring of the fluorenone nucleus.Some syntheses of fluorenones employ fluorene, 11 benzophenone, 12 or hexahydrofluorenone 13a precursors. Unfortunately, these procedures either give isomeric mixtures, are low yielding or offer limited access to certain isomers. Increased accessibility of substituted biphenyls through numerous cross-coupling techniques makes the intramolecular acylation reactions of biphenyl carboxylic acids 11 and biphenyl amides 14 an attractive approach to fluorenones. Of note are the recently reported in situ Suzuki cross-coupling methods which obviate the need for isolation of boronic acid intermediates. 15 Furthermore, the respective cyclization chemistries of biaryl-2-carboxylic acids and biaryl-2-carboxamides, the classical and anionic equivalent of the Friedel-Crafts reaction, are complementary and enable the preparation of a complete isomeric set. In an effort to obtain all possible dihydroxyfluorenone regioisomers 7a-f , we have employed and here report a convenient synthetic approach utilizing, 1) an efficient in situ generation and Pd(0)-catalyzed crosscoupling of aryl boranes to prepare substituted biaryls; 2) regiospecific remote aromatic metalation cyclization; and 3) a complementary Friedel-Crafts acylation cyclization.Thus, 2-bromo-N , N -diethylbenzamide (1a) (Scheme 1) undergoes lithium-halogen exchange and boronation at the 2-position. Treatment of the boronate with dimethoxyaryl bromides and aryl triflates 2a-e under modified in situ Suzuki conditions gave the biarylamides 3a-e . Intramolecular cyclization occurs when 3a-e react with LDA in a remote metalation process as described by Snieckus. 14 The five dimethoxyfluorenone regioisomers 6a-e thus formed are easily demethylated with refluxing HBr/AcOH to give dihydroxyfluorenones 7a-e in good yield.In order to obtain the sixth regioisomer 7f , we employed the same in situ coupling procedure using 2a and oxazoline 1b as a masked carboxylic acid (Scheme 2). Acid hydrolysis of the ring-opened 16 intermediate 4 gave biaryl-2-benzoic acid 5 which underwent normal Friedel-Crafts cyclization to regioselectively provide 2,3-dimethoxyfluoren-9-one (6f) in high yield. 17 Fluorenone 6f cannot be prepared by the anionic equivalent route since the more acidic o...

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Alkamine Esters of Fluorenonecarboxylic Acids¹

Cited by 15 publications

References 0 publications

Clemmensen reduction of 2-acetylfluorene. Pathways for the formation of 2,3-di(2-fluorenyl)butane and its homologues

Clemmensen reduction of 2-acetylfluorene. Pathways for the formation of 2,3-di(2-fluorenyl)butane and its homologues

Metal−Organic Framework Based on [Zn₄O(COO)₆] Clusters: Rare 3D Kagomé Topology and Luminescence

An Efficient Synthesis of Dihydroxyfluorenones via in Situ Pd(0)-Catalyzed Cross-Coupling

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Alkamine Esters of Fluorenonecarboxylic Acids1

Cited by 15 publications

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Clemmensen reduction of 2-acetylfluorene. Pathways for the formation of 2,3-di(2-fluorenyl)butane and its homologues

Clemmensen reduction of 2-acetylfluorene. Pathways for the formation of 2,3-di(2-fluorenyl)butane and its homologues

Metal−Organic Framework Based on [Zn4O(COO)6] Clusters: Rare 3D Kagomé Topology and Luminescence

An Efficient Synthesis of Dihydroxyfluorenones via in Situ Pd(0)-Catalyzed Cross-Coupling

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Alkamine Esters of Fluorenonecarboxylic Acids¹

Metal−Organic Framework Based on [Zn₄O(COO)₆] Clusters: Rare 3D Kagomé Topology and Luminescence