Lewis acid catalyzed cascade reaction of 3-(2-benzenesulfonamide)propargylic alcohols to spiro[indene-benzosultam]s.

A highly efficient and convenient construction of the spiro[indene-benzosultam] skeleton from propargylic alcohols has been developed. The reaction proceeded in a Lewis acid catalyzed cascade process, including the trapping of allene carbocation with sulfonamide, electrophilic cyclization, and intramolecular Friedel-Crafts alkylation. In the presence of NIS or NBS, iodo/bromo-substituted spiro[indene-benzosultam]s could be prepared in excellent yields.

Cu-catalyzed 1,2-dihydroisoquinolines synthesis from o-ethynyl benzacetals and sulfonyl azides.

An efficient synthesis of 1,3-/1,1-dialkoxy 1,2-dihydroisoquinolines from o-ethynylbenzacetals and sulfonyl azides via a cascade process combining copper-catalyzed alkyne-azide cycloaddition (CuAAC), Dimroth rearrangement, 1,5-OR shift/1,5-H shift, and 6π-electrocyclic ring closure (6π-ERC) is described. Extension of the produced 1,3-dialkoxy-1,2-dihydroisoquinolines to isoquinolium salts is also disclosed.

3-Alkenylation or 3-alkylation of indole with propargylic alcohols: construction of 3,4-dihydrocyclopenta[b]indole and 1,4-dihydrocyclopenta[b]indole in the presence of different catalysts.

3-Alkenylation or 3-alkylation of indole with propargylic alcohols could be efficiently controlled by the catalyst. In the presence of triflic acid, 3-alkenylation of indole occurred and a 3,4-dihydrocyclopenta[b]indole skeleton was effectively constructed in moderate to excellent yields via a cascade process. In the presence of Cu(OTf)(2), 3-alkylation of indole resulted in the formation of 3-propargylic indole, which could be further converted into 2-iodo-1,4-dihydrocyclopenta[b]indoles in the presence of N-iodosuccinimide and boron trifluoride etherate. Possible mechanisms related to the 3-alkenylation or 3-alkylation of indole and their extension to the formation of 3,4-dihydrocyclopenta[b]indoles or 1,4-dihydrocyclopenta[b]indoles are postulated and discussed.

Lewis acid-promoted three-component reactions of propargylic alcohols with 2-butynedioates and secondary amines.

We report herein a three-component reaction of propargylic alcohols with 2-butynedioates and secondary amines, which furnished functionalized dihydroazepines. In the cases where benzylmethylamine and benzyl-i-propylamine were used as the secondary amine, the reaction afforded 2,5-dihydro-1H-pyrroles and 2,3-dihydro-1H-pyrroles, respectively, as the major product along with the desired dihydroazepines. The reaction mode depends on the electronic and steric effect of the substitutents on the secondary amines used. A tentative mechanism for this cascade process is postulated. The key intermediate is ascribed to 1,3,4-pentatrien-1-amine, which is formed by trapping the in situ generating allenic carbocation with enamine. Because of the reactivity of 1,3,4-pentatrien-1-amine formed, different products were thus formed.

Three-component synthesis of polysubstituted pyrroles from α-diazoketones, nitroalkenes, and amines.

Polysubstituted pyrroles are regiospecifically synthesized via the copper-catalyzed three-component reaction of α-diazoketones, nitroalkenes, and amines under aerobic conditions. The cascade process involves an N-H insertion of carbene, a copper-catalyzed oxidative dehydrogenation of amine, and a [3 + 2] cycloaddition of azomethine ylide.

Tandem reaction of propargyl alcohol and N-sulfonylhydrazone: synthesis of dihydropyrazole and its utility in the preparation of 3,3-diarylacrylonitrile.

An efficient and straightforward strategy for the synthesis of 4-methylene-1-(phenylsulfonyl)-4,5-dihydro-1H-pyrazole from propargyl alcohol and N-sulfonylhydrazone is described. N-Sulfonyl allenamide is postulated to be the key intermediate for this tandem transformation.

Preparation of allenephosphoramide and its utility in the preparation of 4,9-dihydro-2h-benzo[f]isoindoles.

Allenephosphoramides were prepared from propargyl alcohols and diethyl arylphosphoramides using Yb(OTf)(3) as catalyst. In the presence of iodine, 4,9-dihydro-2H-benzo[f]isoindole derivatives could be efficiently constructed from the same two starting materials in a single step.

Copper-cascade catalysis: synthesis of 3-functionalized indoles.

A three-component reaction of indoles, sulfonyl azides and terminal alkynes afforded 3-functionalized indoles in a single step via copper-cascade catalysis.

Tandem reaction of propargylic alcohol, sulfonamide, and N-iodosuccinimide: synthesis of N-(2-iodoinden-1-yl)arenesulfonamide.

An efficient and straightforward strategy for the synthesis of N-(2-haloinden-1-yl)arenesulfonamides from propargylic alcohols and sulfonamides is described. Allenesulfonamide is postulated to be the key intermediate for this tandem transformation.

Copper-catalyzed tandem nucleophilic ring-opening/intramolecular oxidative amidation of N-tosylaziridines and hydrazones under aerobic conditions.

A novel and efficient copper-catalyzed tandem reaction of N-tosylaziridines and hydrazones under aerobic conditions to afford the functionalized tetrahydrotriazines is described. The process involves a nucleophilic ring-opening and an intramolecular oxidative amidation.

Synthesis of functionalized indenes via cascade reaction of aziridines and propargyl alcohols.

A concise synthesis of functionalized indenes via the Lewis acid catalyzed cascade reaction of aziridines and propargylic alcohols has been developed. The methodology offers great potential for the synthesis of biologically active indene derivatives and related polycyclic compounds.