- The Hexadehydro-Diels-Alder Cycloisomerization Reaction Proceeds by a Stepwise Mechanism
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We report here experiments showing that the hexadehydro-Diels-Alder (HDDA) cycloisomerization reaction proceeds in a stepwise manner - i.e., via a diradical intermediate. Judicious use of substituent effects was decisive. We prepared (i) a series of triyn
- Wang, Tao,Niu, Dawen,Hoye, Thomas R.
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- Hexadehydro-Diels-Alder (HDDA)-Enabled Carbazolyne Chemistry: Single Step, de Novo Construction of the Pyranocarbazole Core of Alkaloids of the Murraya koenigii (Curry Tree) Family
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Here we report the use of the hexadehydro-Diels-Alder (HDDA) reaction for the de novo construction of a benzenoid ring in fused polycyclic heteroaromatic carbazole (i.e., [2,3]-benzoindole) skeletons. The strategy allows creation of highly substituted benzenoids. We also describe the HDDA-enabled chemical synthesis of the natural product alkaloids mahanimbine and koenidine. Trapping of the intermediate carbazolyne with a conjugated enal, proceeding through formal [2+2] cycloaddition, 4π-electrocyclic ring opening, and 6π-electrocyclic ring-closing events, constitutes a robust method for producing pyranocarbazoles.
- Wang, Tao,Hoye, Thomas R.
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- Practical and safe procedures for the preparation of the lower homologues of bromoacetylene
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The lower homologues of bromoacetylene, from 1-bromopropyne to 1-bromo-1-hexyne, have been prepared in excellent yield by stirring the alkyne (in the cases of 1-propyne and 1-butyne a dilute solution in high-boiling petroleum ether) with a very concentrated aqueous solution of potassium hypobromite and potassium hydroxide.
- Brandsma,Verkruijsse
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- Synthesis of 1,3-Diynes via Cadiot-Chodkiewicz Coupling of Volatile, in Situ Generated Bromoalkynes
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A convenient Cadiot-Chodkiewicz protocol that facilitates the use of low molecular weight alkyne coupling partners is described. The method entails an in situ elimination from a dibromoolefin precursor and immediate subjection to copper-catalyzed conditions, circumventing the hazards of volatile brominated alkynes. The scope of this method is described, and the internal 1,3-diyne products are preliminarily evaluated in ruthenium-catalyzed azide-alkyne cycloadditions.
- Knutson, Phil C.,Fredericks, Haleigh E.,Ferreira, Eric M.
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supporting information
p. 6845 - 6849
(2018/10/25)
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- Total Synthesis of Gelsenicine via a Catalyzed Cycloisomerization Strategy
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The first total synthesis of (±)-gelsenicine is reported. The synthetic route is highly efficient (13 steps), featuring (1) a pivotal metal-catalyzed isomerization/rearrangement process that forges the central core of the molecule and (2) two facile C-N bond-forming steps that establish the flanking heterocycles.
- Newcomb, Eric T.,Knutson, Phil C.,Pedersen, Blaine A.,Ferreira, Eric M.
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supporting information
p. 108 - 111
(2016/01/25)
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- Reactions of HDDA-Derived Benzynes with Sulfides: Mechanism, Modes, and Three-Component Reactions
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We report here reactions of alkyl sulfides with benzynes thermally generated by the hexadehydro-Diels-Alder (HDDA) cycloisomerization. The initially produced 1,3-betaine (o-sulfonium/aryl carbanion) undergoes intramolecular proton transfer to generate a more stable S-aryl sulfur ylide. This can react in various manners, including engaging weak acids (HA) in the reaction medium. This can produce transient ion pairs ArSR2+A- that proceed to the products ArSR + RA. When cyclic sulfides are used, A- opens the ring and is incorporated into the product, an outcome that constitutes a versatile, three-component coupling process.
- Chen, Junhua,Palani, Vignesh,Hoye, Thomas R.
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supporting information
p. 4318 - 4321
(2016/05/09)
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- Halogenation of alkynes and alkynylsilanes
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Halogenation of alkynes has given 1,2-dihalogenoalkenes in good yields.Bromination of alkynylsilanes has given 1,2-dibromovinylsilanes, and reactions with iodine chloride mainly iodoalkynes.
- Al-Hassan, Mohammed I.
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p. 183 - 186
(2007/10/02)
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