Synthesis of Cyclohepta[b]indoles and Furo[3,4-b]carbazoles from Indoles, Tertiary Propargylic Alcohols, and Activated Alkynes.

A robust metal-free and environmentally friendly approach to cyclohepta[b]indole and furo[3,4-b]carbazole frameworks via a three-component reaction from indoles, tertiary propargylic alcohols, and activated alkynes is described. A probable mechanism was proposed on the basis of the isolation and characterization of a key intermediate of the reaction. A gram-scale reaction and product derivatizations were also performed to demonstrate the practicality of the developed methodology.

Synthesis of pyrano[3,2-c]quinolones and furo[3,2-c]quinolones via acid-catalyzed tandem reaction of 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols.

Two acid-catalyzed tandem reactions between 4-hydroxy-1-methylquinolin-2(1H)-one and propargylic alcohols are described. Depending mainly on the propargylic alcohol used, these tandem reactions proceed via either a Friedel-Crafts-type allenylation followed by 6-endo-dig cyclization sequence to form pyrano[3,2-c]quinolones or a Friedel-Crafts-type alkylation and 5-exo-dig ring closure sequence to afford furo[3,2-c]quinolones in moderate-to-high yields. The pyrano[3,2-c]quinolones products could be further transformed to tetracyclic 4,9-dihydro-5H-cyclopenta[lmn]phenanthridin-5-one derivatives.

Synthesis of tetrahydro-ß-carbolines from 2-indolylmethyl azides and propargylic alcohols.

A facile and efficient route to tetrahydro-ß-carbolines from 2-indolylmethyl azides and propargylic alcohols via acid-catalyzed dehydrative annulation reactions is described. This reaction proceeds through a cascade sequence of Friedel-Crafts-type alkylation followed by intramolecular "Click" reaction, involving the formation of multiple chemical bonds in a single operation with excellent atom-economy and broad functional group tolerance.

Synthesis of polysubstituted 1,2-dihydroquinolines and indoles via cascade reactions of arylamines and propargylic alcohols catalyzed by FeCl3·6H2O.

An efficient, environmentally friendly and high-yielding route from inexpensive starting materials to 1,2-dihydroquinolines has been developed. This procedure proceeded via a cascade Friedel-Crafts-type reaction and 6-endo-trig hydroamination under the catalysis of FeCl3·6H2O, involving the formation of two new σ (C-C and C-N) bonds in a single operation for the construction of a 1,2-dihydroquinoline skeleton in good to excellent yields.

Copper(I)-Catalyzed Kinetic Resolution of N-Sulfonylaziridines with Indoles: Efficient Construction of Pyrroloindolines.

The first Lewis acid catalyzed [3 + 2] annulation of indoles and 2-aryl-N-tosylaziridines was realized by using copper(I)/chiral diphosphine complexes as a catalyst. With this method, a variety of uniquely substituted chiral pyrroloindolines bearing multiple contiguous stereogenic centers were facilely accessed in a straightforward, high-yielding, and highly stereoselective way under mild conditions.

Lewis acid catalyzed cascade reaction to carbazoles and naphthalenes via dehydrative [3 + 3]-annulation.

A novel Lewis acid catalyzed dehydrative [3 + 3]-annulation of readily available benzylic alcohols and propargylic alcohols was developed to give polysubstituted carbazoles and naphthalenes in moderate to good yields with water as the only byproduct. The reaction was presumed to proceed via a cascade process involving Friedel-Crafts-type allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner-Meerwein rearrangement.

Synthesis of polysubstituted pyrroles via [3 + 2]-annulation of aziridines and ß-nitroalkenes under aerobic conditions.

Polysubstituted pyrroles were regioselectively synthesized in moderate to good yields via the copper acetate-catalyzed [3 + 2] annulation reaction of readily accessible aziridines and nitroalkenes. This reaction was proposed to proceed through a key azomethine ylide intermediate generated by selective C-C bond cleavage of the aziridine followed by annulation with nitroalkenes under aerobic conditions.

Synthesis, structure, and reactivity of lanthanide complexes incorporating indolyl ligands in novel hapticities.

The chemistry of interactions of 2-(2,6-diisopropylphenylaminomethylene)indole ligand (1) with europium and ytterbium amides is described. Reaction of 2-(2,6-diisopropylphenylaminomethylene)indole 2-(2,6-i-Pr2C6H3NHCH2)C8H5NH (1) with europium amide [(Me3Si)2N]3Eu(III)(µ-Cl)Li(THF)3 afforded a novel europium(II) complex formulated as {[µ-η(6):η(1):η(1)-2-(2,6-i-Pr2C6H3N═CH)C8H5N]Eu[2-(2,6-i-Pr2C6H3N═CH)C8H5N]}2 (2), having a bridged indolyl ligand in the novel µ-η(6):η(1):η(1) hapticities with the reduction of europium(III) to europium(II) and the oxidation of amino to imino group. Reaction of 2-(2,6-diisopropylphenylaminomethylene)indole 2-(2,6-i-Pr2C6H3NHCH2)C8H5NH (1) with ytterbium(III) amide [(Me3Si)2N]3Yb(III)(µ-Cl)Li(THF)3 produced the only deprotonated ytterbium(III) complex formulated as [2-(2,6-i-Pr2C6H3NCH2)C8H5N]Yb[N(SiMe3)2](THF)2 (3), having an η(1) hapticity indolyl ligand. Reaction of 2 with formamidine [(2,6-Me2C6H3)NCHNH(C6H3Me2-2,6)] produced {[µ-η(3):η(1):η(1)-2-(2,6-i-Pr2C6H3N═CH)C8H5N]Eu[(2,6-Me2C6H3)NCHN(C6H3Me2-2,6)](THF)}2 (4), which has a bridged indolyl ligand in the novel µ-η(3):η(1):η(1) hapticities, whereas the reaction of 2 with the more sterically bulky formamidine [(2,6-i-Pr2C6H3)NCHNH(C6H3i-Pr2-2,6)] afforded complex {[µ-η(2):η(1):η(1)-2-(2,6-i-Pr2C6H3N═CH)C8H5N]Eu[(2,6-i-Pr2C6H3)N═CHN(C6H3i-Pr2-2,6)](THF)}2 (5), having the indolyl ligand in the novel µ-η(2):η(1):η(1) hapticities. The results represent the first example of organometallic complexes having indolyl ligands in the novel µ-η(6):η(1):η(1), µ-η(3):η(1):η(1), and µ-η(2):η(1):η(1) bonding modes with metal.

A novel Lewis acid catalyzed [3 + 3]-annulation strategy for the syntheses of tetrahydro-ß-carbolines and tetrahydroisoquinolines.

A novel Lewis acid catalyzed [3 + 3]-annulation process for the efficient syntheses of both tetrahydro-ß-carbolines and tetrahydroisoquinolines from readily available benzylic alcohols and aziridines was developed, which would be a highly valuable complement to the widely used Pictet-Spengler reaction. A probable mechanism was proposed based on the isolation and characterization of two key intermediates. This strategy enables facile access to important alkaloid frameworks not easily available with other known methods.

Rare-earth metal complexes having an unusual indolyl-1,2-dianion through C-H activation with a novel η1:(µ2-η1:η1) bonding with metals.

Studies on the reactions of 3-(tert-butyliminomethine)indole or 3-(tert-butylaminomethylene)indole with rare-earth metal amides [(Me(3)Si)(2)N](3)RE(III)(µ-Cl)Li(THF)(3) (RE = Y, Yb) led to the discovery of different reactivity patterns with isolation of novel rare-earth metal complexes having a unique indolyl-1,2-dianion in a novel η(1):(µ(2)-η(1):η(1)) bonding mode through C-H activation.

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.