Sequential condensation and double desulfonylative cyclopropanation of 1,2-bis(sulfonylmethyl)arenes with 3-arylacroleins: access to biscyclopropane-fused tetralins.

Efficient tBuOK-mediated sequential condensation and double desulfonylative cyclopropanation of readily accessible 1,2-bis(sulfonylmethyl)arenes with 3-arylacroleins is described. This high-yielding, single-step strategy provides a variety of polysubstituted biscyclopropane-fused tetralins with six contiguous stereogenic centers via the construction of five carbon-carbon single bonds. A plausible mechanism is proposed and discussed. In the overall reaction process, water and sulfinic acid salts were generated as the byproducts.

Tandem C- and O-alkylative annulation of ß-ketosulfones with 1,2-bisbromomethyl arenes: one-pot construction of sulfonyl indanes and dioxadibenzofused macrocycles.

Herein, a tandem synthetic route for constructing sulfonyl indanes and dioxadibenzofused macrocycles is described. This strategy involves a transition-metal-free, base-mediated tandem C- and O-alkylative annulation of ß-ketosulfones with 1,2-bisbromomethyl arenes with moderate to excellent yields under open-vessel reaction conditions. In the overall reaction process, two carbon-carbon (C-C) and two carbon-oxygen (C-O) bonds are formed. Various base-promoted reaction conditions are screened for this one-pot easy-to-operate conversion.

Tandem cyclocondensation of 1,3-bis-sulfonylpropan-2-ones with arylaldehydes. One-pot synthesis of tris-sulfonyl 3-arylphenols.

One-pot tandem piperidinium acetate-mediated cyclocondensation of 1,3-bis-sulfonylpropan-2-ones with arylaldehydes generates tris-sulfonyl 3-arylphenols in moderate to good yields in refluxing toluene under easy-operational reaction conditions. A plausible mechanism is proposed and discussed. In the overall reaction process, water and sulfinic acid were generated as the byproducts. Various ammonium carboxylate-promoted conditions are investigated for one-pot [3 + 2 + 1]-benzannulation.

BF3·OEt2-mediated nucleophilic fluorocyclization of sulfonyl 3-methylene-oxabenzocyclooctan-6-ones. Diastereocontrolled synthesis of benzofused fluorooxabicyclo[4.2.1]nonanes.

We describe a facile-operational, high-yield method for the diastereocontrolled preparation of novel sulfonyl benzofused fluorooxabicyclo[4.2.1]nonanes by a straightforward synthetic route, including (i) NaBH4-mediated reduction of sulfonyl 3-methylene-oxabenzocyclooctan-6-ones and (ii) BF3·OEt2-mediated intramolecular nucleophilic fluorocyclization. The plausible mechanism for the preparation is proposed and discussed. This protocol can easily install a fluoro-atom on the bridged head position in a short time and under mild conditions, resulting in one carbon-carbon and one carbon-fluorine bond formation.

HCl-mediated cascade cyclocondensation of oxygenated arylacetic acids with arylaldehydes: one-pot synthesis of 1-arylisoquinolines.

In this paper, a concise, open-vessel synthesis of 1-arylisoquinolines is described via HCl-mediated intermolecular cyclocondensation of oxygenated arylacetic acids with arylaldehydes in the presence of NH2OH and alcoholic solvents under mild and one-pot reaction conditions. A plausible mechanism is proposed and discussed herein. In the overall reaction process, only water was generated as the byproduct. Various environmentally friendly reaction conditions are investigated for convenient transformation via the (4C + 1C + 1N) annulation. This protocol provides a highly effective ring closure via the formations of one carbon-carbon (C-C) bond, two carbon-nitrogen (C-N) bonds and one carbon-oxygen (C-O) bond.

Construction of Sulfonyl Dihydrobenzo[c]xanthen-7-ones Core via NH4OAc/PdCl2/CuCl2-Mediated Double Cyclocondensation of α-Sulfonyl o-Hydroxyacetophenones with 2-Allylbenzaldehydes.

NH4OAc/PdCl2/CuCl2 mediated domino double cyclocondensation of α-sulfonyl o-hydroxyacetophenones and 2-allylbenzaldehydes provides tetracyclic sulfonyl dihydrobenzo[c]xanthen-7-one core with good to excellent yields in MeOH. The intermediates contain a 3-sulfonyl flavanone motif. Only water is generated as a byproduct. The use of various catalysts and reaction conditions is studied for the facile-operational conversion.

Construction of Sulfonyl Oxabenzo[3.3.1]bicyclic Core via Cyclocondensation of ß-Ketosulfones and o-Formyl Allylbenzenes.

NH4OAc mediated domino Knoevenagel/Diels-Alder cyclocondensation of ß-ketosulfones 1 and o-formyl allylbenzenes 2 provides sulfonyl oxabenzo[3.3.1]bicyclic core 4 in a cosolvent of toluene and HOAc (v/v = 1/1) at reflux for 3 h. The intermediate 3 contains a chalcone motif. The uses of various ammonium salts and solvent systems are investigated for facile and efficient transformation. The plausible mechanisms have been proposed and the DFT calculations have been included.

Bi(OTf)3-Mediated Intramolecular Olefinic Cyclization: Synthesis of Substituted Aryl-Dihydronaphthalenes and Indenes.

In this article, a facile two-step and one-pot synthetic route for the preparation of substituted aryl dihydronaphthalenes starting from 2-allylbenzaldehydes via Grignard 1,2-addition and Bi(OTf)3-catalyzed intramolecular olefinic cyclization has been developed. A five-membered ring indene skeleton is also prepared via olefin isomerization, 1,2-addition followed by cyclization. Some key structures are determined using single-crystal X-ray crystallography. A possible mechanism is presented herein.