Diels-Alder/Ene Reactivities of 2-(1'-Cycloalkenyl)thiophenes and 2-(1'-Cycloalkenyl)benzo[b]thiophenes with N-Phenylmaleimides: Role of Cycloalkene Ring Size on Benzothiophene and Dibenzothiophene Product Distributions.

Scaffolds of thiophene and benzothiophene are the important class of bioactive compounds found abundant in nature. The Diels-Alder reactions of 2-(1'-cycloalkenyl)thiophenes and 2-(1'-cycloalkenyl)benzo[b]thiophenes having the alkene groups present in five-, six-, seven-, eight-, and twelve-membered rings with substituted N-phenylmaleimides are characterized. The size of the cycloalkene rings plays a critical role in dictating the product distributions of expected and isomerized Diels-Alder adducts. 2D NMR studies indicate that the isolated isomers for 2-(1'-cycloalkenyl)thiophenes having five-, six-, and seven-membered rings are aromatized benzothiophene products, whereas eight- and twelve-membered rings are un-rearranged adducts. In addition, the product of subsequent ene-reaction with the N-phenylmaleimide is isolated for the five- and six-membered ring cases. Interestingly, in the 2-(1'-cycloalkenyl)benzo[b]thiophene having five-, six-, seven-, eight-, and twelve-membered rings, the un-rearranged dibenzothiophene Diels-Alder adduct is isolated in every instance. Molecular mechanics and density functional theory (M06-2X and PBE0-D3) calculations are performed to understand the differential reactivity of the various dienes for both the initial Diels-Alder reaction and a possible, subsequent ene reaction.

Oxidative conversion of δ-sultones to γ-lactones.

Delta-sultones, prepared by C-H insertion, can be oxidatively converted to gamma-lactones by treatment with t-BuOK/t-BuOOH. An intermediate in the synthesis of (-)-eburnamonin was prepared using this approach.

Synthesis of plakortethers F and G.

Synthesis of plakortethers F and G has been performed by taking advantage of the symmetry in the structure. The structures of the prepared compounds have been confirmed by COSY, 1D NOE, and chemical transformation studies. The synthetic plakortether F was found to match the natural product by all physical data. The synthetic plakortether G exhibited several disagreements in (13)C NMR data with the reported values. However, on the basis of an extremely close match in appearance of its (1)H NMR spectrum to the obtained (1)H NMR spectrum of the natural product, as well as matching optical rotations, the two compounds are believed to be identical.

Formation of six- vs. five-membered cyclic sulfones by C-H insertion.

Selectivity of six- vs. five- membered ring formation in C-H insertion on alkylsulfonyl diazoacetates is sensitive to the substrate structure and catalyst used.

Enantioselective synthesis of Bakuchiol using diazosulfonate C-H insertion to install the quaternary center.

Bakuchiol was prepared from commercial (-)-citronellol using the diazosulfonate C-H insertion to control the regioselectivity and install the quaternary center.

Selective formation of six-membered cyclic sulfones and sulfonates by C-H insertion.

[reaction: see text] Carbethoxy diazosulfones and sulfonates, easily available from corresponding sulfones and sulfonates, undergo C-H insertion with preferential formation of six membered cyclic sulfones and sulfonates.

SYNTHETICALLY USEFUL INTERMEDIATES BY DIAZOSULFONE AND SULFONATE C-H INSERTION.

Intramolecular C-H insertion on diazosulfone and diazosulfonate substrates was used to prepare synthetically useful intermediates from easily available starting materials.

PRACTICAL PREPARATION OF RESVERATROL 3-O-ß-D-GLUCURONIDE.

A practical synthesis of resveratrol 3-O-ß-D-glucuronide, suitable for preparation of large quantities, was developed using selective deacetylation of resveratrol triacetate with ammonium acetate. A simplified procedure for large scale preparation of resveratrol is also reported.

Sulfur ylide-initiated thio-claisen rearrangements. The synthesis of highly substituted indolines.

The coupling of rhodium carbenoids from vinyl diazoacetates with 2-thio-3-alkyl indoles was found to generate C(3) quaternary substituted indolines via a thionium ylide-initiated [3,3]-sigmatropic rearrangement.