192431-31-5Relevant academic research and scientific papers
ENANTIOSELECTIVE CROSS DEHYDROGENATIVE COUPLING REACTIONS AND COMPOUNDS SYNTHESIZED BY THE REACTIONS
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Paragraph 0118; 0138; 0395-0396, (2020/07/04)
Disclosed are enantioselective cross dehydrogenative coupling reactions for synthesizing tetrahydropyran compounds. Novel tetrahydropyran compounds may be synthesized by the disclosed methods as well as tetrahydropyran precursor compounds for synthesizing various naturally occurring compounds. The enantioselective cross dehydrogenative coupling reactions utilize in situ Lewis Acid activation in combination with oxidative formation of an oxocarbenium ion to provide a highly efficient and selective coupling reaction for synthesizing tetrahydropyran compounds.
Synthesis of arylnaphthalene lignan scaffold by gold-catalyzed intramolecular sequential electrophilic addition and benzannulation
Gudla, Vanajakshi,Balamurugan, Rengarajan
experimental part, p. 9919 - 9933 (2012/01/15)
An intramolecular approach to generate compounds containing an arylnaphthalene lignan scaffold in high yields is presented. It involves a sequential intramolecular electrophilic attack of carbonyl on arylalkyne followed by benzannulation catalyzed by gold salt. AuCl3 in combination with AgSbF6 works better to effect this transformation. Selected products have been converted into arylnaphthalene lactone natural products such as justicidin E, taiwanin C, and retrojusticidin B (Figure presented).
Gold-catalysed activation of epoxides: Application in the synthesis of bicyclic ketals
Balamurugan, Rengarajan,Kothapalli, Raveendra Babu,Thota, Ganesh Kumar
supporting information; experimental part, p. 1557 - 1569 (2011/04/25)
Gold-catalysed generation of diol equivalents from epoxides and their intramolecular reaction with Ca≡C bonds to generate bicyclic ketals is presented. This reaction essentially involves the formation of an acetonide, which subsequently cyclises on the alkyne intramolecularly under gold catalysis conditions. This method could be extended to make optically pure bicyclic ketals. Deuterium incorporation experiments were carried out to ascertain the mechanism of the reaction. Sequential activation of epoxide and alkyne moieties by a gold catalyst in acetone as solvent has been achieved. This strategyhas been employed to synthesise bicyclic ketals from epoxy alkynes. Copyright
Stereoselective Cyclizations and Rearrangements in Vinyl Radicals Promoted by Regioselective Sulfanyl Radical Addition to Enynes
Montevecchi, Pier Carlo,Navacchia, Maria Luisa
, p. 5600 - 5607 (2007/10/03)
Regioselective radical addition of 4-cyanotoluenethiol (1a) to enynes 3-6 leads to vinyl radicals 7-10 that can undergo five- or six-membered cyclization onto styrene or terminal double bonds in competition with 5-exo cyclization onto the aryl ring. The latter affords spiro-cyclohexadienyl radical intermediates which can either be trapped by 2-cyanoisopropyl radicals or give 1,4-aryl migration products. Regioselective radical addition of phenethanethiol (1b) to enynes 3-6 gives radicals 11-14 which undergo five- or six-membered cyclization onto the alkene double bond; the stereoelectronically disfavored 6-exo cyclization can compete with intermolecular hydrogen abstraction and (to a small extent) with 1,5-hydrogen migration. The 5- and 6-(π-exo)exo cyclization of vinyl radicals 7, 9, 11-13 is highly stereoselective and exclusively or predominately affords products deriving from the (Z)-isomers. Stereochemical evidence indicates that the six-membered endo-cyclization products 30 and 50 could derive from a direct 6-endo cyclization of (E)-radicals (E)-10 and (E)-14 rather than from a 5-exo cyclization/ring expansion process. Sulfanyl radical addition to enynes 3-5 is highly regioselective to the terminal triple bond. In contrast, reaction of thiols 1a,b with enyne 6 leads to products deriving from sulfanyl radical addition to both the CC triple and double bond. This behavior is accounted for by assuming that sulfanyl radical addition to the alkyne triple bond is not reversible, while the addition to the alkene double bond is. Vinyl radical 10 affords product 33 by a rare 1,4-hydrogen migration/fragmentation process.
