- Synthetic methodology to prepare polysubstituted 2-aminopyrans. Synthesis of the C32–C38 subunit of immunosuppressant sanglifehrin A
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Pyranic hemiaminal synthons are present in natural and unnatural products with biological activity. Here a synthetic pathway to prepare this type of intermediates is presented. The methodology is based on three main steps: a) The [4+3] cycloaddition reaction of an α,α'-dihaloketone and a conveniently protected 2-aminofuran diene. b) Chemical modification of the resulting oxabicyclic cycloadduct and orthogonal protection of organic functions, and c) Reductive ozonolysis of the C6–C7 double bond of the modified cycloadduct to afford a pentasubstituted polyfunctionalized pyranic hemiaminal ester with up to 94% yield. When working with 2,4-dibromo-3-pentanone and 2-tert-butoxycarbonylaminofuran as starting materials, the C32–C38 subunit of immunosuppressant sanglifehrin A was obtained with excellent yield.
- Monta?a, ángel M.,Barcia, Joan,Corominas, Albert
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- Synthesis of 3-aminotropones from N-boc-protected furan-2-amine (=tert-butyl furan-2-ylcarbamate; Boc=(tert-butoxy)carbonyl) by cycloaddition reactions and subsequent rearrangement
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The 3-aminotropones (= 3-aminocyclohepta-2,4,6-trien-1-ones) 4 were prepared in two steps by i) a [4+3] cycloaddition reaction between a conveniently substituted α,α′-dihalo ketone 1 and a furan-2-amine derivative 2 functionalized at C(2) by a protected amino group (→3), and ii) a base-induced molecular rearrangement of the cycloadduct 3 via cleavage of the O-bridge. A mechanism for the formation of 3-aminotropones is proposed on the basis of the initial deprotonation of the [(tert-butoxy) carbonyl]amino (BocNH) group of 3, followed by O-bridge opening, an acid - base equilibrium, and finally an alkoxyaluminate elimination to afford the conjugated stable troponoid system (Scheme 7).
- Montana, Angel M.,Barcia, Juan A.,Kociok-Koehn, Gabriele,Font-Bardia, Merce,Solans, Xavier
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- Formation of 6-Azaindoles by Intramolecular Diels-Alder Reaction of Oxazoles and Total Synthesis of Marinoquinoline A
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A new variant of the intramolecular Diels-Alder oxazole (IMDAO) cycloaddition that provides direct access to 6-azaindoles was developed. The IMDAO reaction was applied in a total synthesis of the aminophenylpyrrole-derived alkaloid marinoquinoline A, also
- Jhaveri, Dishit P.,Osano, Mana,Wipf, Peter
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supporting information
p. 2215 - 2219
(2020/04/09)
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- Base-Mediated Intramolecular Decarboxylative Synthesis of Alkylamines from Alkanoyloxycarbamates
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A general and effective method for the synthesis of alkylamine via intramolecular decarboxylation of alkanoyloxycarbamates is described. The alkanoyloxycarbamates are readily prepared with alkyl carboxylic acids and hydroxylamine. The reaction shows a broad range of substrates (primary and secondary alkyl) with functional tolerance, and the corresponding products were obtained in good yields under mild conditions.
- Li, Peihe,Ma, Nuannuan,Wang, Zheng,Dai, Qipu,Hu, Changwen
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p. 8233 - 8240
(2018/05/31)
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- Indole synthesis by palladium-catalyzed tandem allylic isomerization-furan Diels-Alder reaction
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A Pd(0)-catalyzed elimination of an allylic acetate generates a π-allyl complex that is postulated to initiate a novel intramolecular Diels-Alder cycloaddition to a tethered furan (IMDAF). Under the reaction conditions, this convergent, microwave-accelerated cascade process provides substituted indoles in moderate to good yields after Pd-hydride elimination, aromatization by dehydration, and in situ N-Boc cleavage.
- Xu, Jie,Wipf, Peter
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supporting information
p. 7093 - 7096
(2017/09/07)
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- New methodology for the synthesis of tetrahydrofuro[3,2-b]furan-2(3H)-one derivatives, synthons of natural products with biological interest
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A new methodology is presented to synthesize in a regio and stereoselective manner tetrahydrofuro[3,2-b]furan-2(3H)-one, structural subunit present in a wide variety of natural products present in plant, fungi, algae, insects, and other living organisms.
- Monta?a, ángel M.,Barcia, Joan A.,Grima, Pedro M.,Kociok-K?hn, Gabriele
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p. 6794 - 6806
(2016/10/04)
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- PROCESSES FOR PREPARING ISOINDOLINE-1,3-DIONE COMPOUNDS
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Provided herein are processes for preparing an isoindoline- 1.3-dione compound, or an enantiomer or a mixture of enantiomers thereof; or a pharmaceutically acceptable salt, solvate, hydrate, or polymorph thereof.
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Paragraph 00192; 00193
(2014/02/16)
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- Investigation of the thermal self-healing mechanism in a cross-linked epoxy system
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The mechanism of self-healing of a cross-linked epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) and a new diamine cross-linker with two Diels-Alder (DA) adducts has been investigated. The location of the DA adducts on the diamine means that the cross-linker is the structural element that can be thermally cleaved and reformed, thereby allowing the cross-linked polymer to flow and fill or heal cracks and scratches. Since the stimulus for opening up the cross-linked network to allow flow and heal is heat, the temperature of the original network cure also becomes an important variable, and in this work different curing conditions have been explored to find suitable curing conditions which can cause the epoxy-amine to react, whilst avoiding initial scission of the DA adducts. The thermal self-healing mechanism of cured samples was studied by following the effect of scission on a range of properties such as the chemistry of the adducts, the glass transition of the polymer network, the size of units into which the network fragments upon scission and the ability of the network to swell. The appropriate conditions required to heal surface scratches of a micrometre size-scale were also studied. The Royal Society of Chemistry 2013.
- Bai, Nan,Simon, George P.,Saito, Kei
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p. 20699 - 20707
(2013/11/06)
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- A facile synthesis of 5-alkoxypyrrol-2(5H)-ones using a modified aza-Achmatowicz oxidation
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An efficient approach to 2,4-disubstituted pyrroles has been uncovered and is based on an oxidative rearrangement of a furanyl carbamate followed by sequential reaction of the resulting 5-methoxypyrrol-2(5H)-one with various alkyl lithiates. The final ste
- Kiren, Sezgin,Hong, Xuechuan,Leverett, Carolyn A.,Padwa, Albert
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scheme or table
p. 6720 - 6729
(2011/03/17)
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- Novel liquid-crystalline mesogens and main-chain chiral smectic thiol-ene polymers based on trifluoromethylphenyl moieties
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The synthesis and characterization of a series of novel liquid-crystalline molecules containing a trifluoromethylphenyl core or a 2,3-bis(trifluoromethyl) phenyl core is described. All trifluoromethylphenyl-containing compounds (W530, W551, and W558) have mesomorphic properties while 2,3-bis(trifluoromethyl) phenyl-containing compounds (W555, W556, W557) are room-temperature crystals without mesophases. Thereafter, based on the chemical structure of W558, to pursue a mesogen with a large electroclinic effect in the SmA* phase for development into electromechanical actuators, a chiral smectic thiol-ene monomer (K0901) is synthesized and polymerized in organic solvents. The polymer is characterized by GPC, DSC, PLM, XRD and shows an expected I-SmA* -Glass phase sequence though the electroclinic effect is relatively small.
- Yang, Hong,Wang, Lixing,Shao, Renfan,Clark, Noel A.,Ortega, Josu,Etxebarria, Jesus,Albouy, Pierre-Antoine,Walba, David M.,Keller, Patrick
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scheme or table
p. 7208 - 7215
(2010/05/18)
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- Stereoselective reductions of N-Boc-hexahydro-1H-indolin-5(6H)-ones
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We report the divergent effects of a 3a-methyl and 3a-phenyl substituent on the chemoselectivity and stereoselectivity of reduction of the enamide moiety of N-Boc-hexahydro-1H-indolin-5(6H)-ones. Under ionic reduction conditions (triethylsilane/trifluoroacetic acid) the enamide group of 3a-methyl-N-Boc-hexahydro-1H-indolin-5(6H)-one was reduced to afford exclusively a cis ring-fused product. For the 3a-phenyl substituted analogue more forcing conditions (sodium cyanoborohydride at pH 2-2.5) were required and resulted in the selective reduction of the enamide group to give a trans ring-fused product as well as reduction of the ketone group.
- Brodney, Michael A.,Cole, Marcus L.,Freemont, Jamie A.,Kyi, Stella,Junk, Peter C.,Padwa, Albert,Riches, Andrew G.,Ryan, John H.
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p. 1939 - 1943
(2007/10/03)
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- Diels-Alder Reaction of 2-Amino-Substituted Furans as a Method for Preparing Substituted Anilines
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5-Amino-2-furancarboxylic acid methyl ester undergoes a facile Diels-Alder cycloaddition with a variety of dienophiles to afford ring-opened cycloadducts that are readily dehydrated using BF3-OEt2 to give polysubstituted anilines. In each case, the cycloaddition proceeds with high regioselectivity, with the electron-withdrawing group being located ortho to the amino group. The most favorable FMO interaction is between the HOMO of the furanamine and the LUMO of the dienophile. The atomic coefficient at the ester carbon of the furan is larger than that at the amino center, and this nicely accommodates the observed regioselectivity. The [4 + 2]-cycloaddition of N-(5-nitrofuranyl)morpholine with methyl vinyl ketone affords a mixture of three phenols. One of the phenols is derived from a Diels - Alder reaction followed by nitro group ejection and subsequent aromatization. The remaining two phenols are the result of cleavage of the initially formed oxabicyclic intermediate with concomitant migration of the nitro group. The mild reaction conditions with which furan-2-carbamic acid tert-butyl ester undergoes Diels - Alder cycloaddition with N-phenylmaleimide allow for the ready isolation of the initial oxybridged cycloadduct.
- Padwa, Albert,Dimitroff, Martin,Waterson, Alex G.,Wu, Tianhua
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p. 4088 - 4096
(2007/10/03)
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