In this paper, we document the construction of functionalized and fused eight-membered carbocycles by the triflic anhydride-mediated cyclization of 7-enamides. Taking advantage of the high ...electrophilicity of the nitrilium ion intermediates, generated in situ from secondary
-(2,6-dimethyl)anilides, the nonactivated, trisubstituted alkene-nitrilium cyclization reactions proceeded smoothly to afford nonconjugated β,γ-enimines (for fused 6/6/8 ring systems), conjugated α,β-enimines (for 6/5/8), or fused 5/8 ring systems in good yields. When the cyclization reactions were followed by one-pot acidic hydrolysis, the reaction led directly to the corresponding α,β-enones. For some substrates, the reaction afford an efficient access to pendent cyclic β,γ-enimines/enones.
An efficient arylsulfonylation/cyclization of 2-aryl-
-methacryloyl indoles with potassium metabisulfite and aryldiazonium tetrafluoroborates was developed. A series of variously substituted ...arylsulfonyl indolo2,1-
isoquinolin-6(5
)-ones were formed in moderate to good yields
utilization of the nature abundant inorganic salt potassium metabisulfite as a SO
surrogate. Additionally, this three-component protocol can also be employed for the synthesis of arylsulfonyl-substituted benzimidazo-2,1-
isoquinolin-6(5
)-ones.
A simple and low-cost tandem sulfonylation/cyclization of 1,5-diene, aryldiazonium salt, and DABCO·(SO2)2 is disclosed. This base-promoted multicomponent reaction can provide a “green” and economic ...synthesis of sulfonylated pyrrolidones under transition-metal-free and moisture/oxygen-insensitive reaction conditions, thus delivering a wide range of sulfonylated pyrrolidones in moderate to high yields with excellent functional group compatibility. A plausible mechanism involving a radical process is proposed, which demonstrates highly chemoselective trapping of the aryl radical with “SO2” species, and a regioselective sulfonylation/cyclization protocol in this reaction.
A new polyene cyclization strategy exploiting β-ionyl derivatives was developed. Photoinduced deconjugation of the extended π-system within these chromophores unveils a contrathermodynamic polyene ...that engages in a Heck bicyclization to afford 4.4.1-propellanes. This cascade improves upon the limited regioselectivity achieved using existing biomimetic tactics and tolerates both electron-rich and electron-deficient (hetero)aryl groups. The utility of this approach was demonstrated with the diverted total synthesis of taxodione and salviasperanol, two isomeric abietane diterpenes that were previously inaccessible along the same synthetic pathway.
Daphenylline is a structurally unique member of the triterpenoid
natural alkaloids, which exhibit intriguing biological activities. Six total syntheses have been reported, five of which utilize ...aromatization approaches. Herein, we report a concise protecting-group-free total synthesis by means of a novel intramolecular oxidative dearomatization reaction, which concurrently generates the critical seven-membered ring and the quaternary-containing vicinal stereocenters. Other notable transformations include a tandem reductive amination/amidation double cyclization reaction, to assemble the cage-like architecture, and installation of the other two chiral stereocenters via a highly enantioselective rhodium-catalyzed challenging hydrogenation of the diene intermediate (90% e.e.) and an unprecedented remote acid-directed Mukaiyama-Michael reaction of the complex benzofused cyclohexanone (13:1 d.r.).
A tandem addition/cyclization reaction between trifluoromethyl N-acylhydrazones and cyanamide is described, which provides a novel and efficient process for the synthesis of polysubstituted ...3-trifluoromethyl-1,2,4-triazolines and their derivatives. The method has the advantages of mild reaction conditions, a broad substrate scope, good product yields, and atom economy.
An efficient I
-promoted one-pot one-step three-component reaction for the synthesis of sulfhydryl indolizines from methyl ketones, 2-pyridylacetate derivatives, and sulfonyl hydrazides via an in ...situ cyclization-rethiolation strategy has been developed. This protocol shows excellent substrate compatibility, including for chain and cyclic aliphatic methyl ketones, natural product pregnenolone acetate, and phosphorus-containing methyl ketones, affording a series of valuable aliphatic-substituted indolizines in good yields.
Herein we reported a Mn(OAc)
2H
O promoted radical sulfonation from functionalized alkenes and potassium metabisulfite (K
S
O
). The reaction realized the construction of oxindole, quinolinone, ...isoquinoline-1,3-dione, or benzoxazine structural fragments and the introduction of sulfonic moieties in one step. More than 50 heterocyclic sulfonates or their derivatives with various substituents were successfully prepared with high efficiency under mild conditions.
Naphthothiophenes were prepared from commercially available 2,3-dibromothiophenes in two steps by one-pot Suzuki/Sonogashira or Sonogashira/Suzuki coupling reactions, followed by intramolecular ...alkyne-carbonyl-metathesis reactions. The final cyclization reaction proceeds in the presence of p-toluenesulfonic acid and provides a rapid access to two series of isomeric naphthothiophenes.
A method for the preparation of 3-alkylated spiro4.5trienones via alkylation/ipso-cyclization of activated alkynes with 4-alkyl-DHPs under transition-metal-free conditions is proposed. This ...alkylation successively undergoes the generation of alkyl radicals, addition of alkyl radicals to the alkynes, and intramolecular ipso-cyclization. The mechanism studies suggest that the alkylation/ipso-cyclization involves a radical process. This ipso-cyclization procedure shows a series of advantages, such as accessibility, mild conditions, high efficiency, greater safety, and an environmentally friendly method.
