ELECTROPHILE MEDIATED HETEROATOM CYCLIZATIONS ONTO C-C π-BONDS. PART 2: METAL ION MEDIATED CYCLIZATION

A new strategy for the synthesis of pyridines from N-propargylic β-enaminothiones

A new robust method for the synthesis of 2,4,5-trisubstituted pyridines with high efficiency and broad functional group tolerance is described.

7-endo selenocyclization reactions on chiral 3-prenyl and 3-cinnamyl-2-hydroxymethylperhydro-1,3-benzoxazine derivatives. A way to enantiopure 1,4-oxazepanes

Enantiopure 1,4-oxazepane derivatives have been prepared by selenocyclofunctionalization of chiral 3-prenyl- and 3-cinnamyl-2-hydroxymethyl-substituted perhydro-1,3-benzoxazine derivatives. The 7-endo-cyclization occurs in high yields and diastereoselection. The regio- and stereochemistry of the cyclization products was dependent on the substitution pattern of the double bond, the nature of the hydroxyl group and the experimental conditions.

Asymmetric Synthesis of (+)-Iso-6-Cassine via Stereoselective Intramolecular Amidomercuration

The first asymmetric synthesis of (+)-iso-6-cassine is described. Lipase-catalyzed resolution, enantioselective Overman rearrangement, and diastereoselective intramolecular amidomercuration were used for the installation of the three stereocenters in (+)-iso-6-cassine, and cross-metathesis was employed for the attachment of the side-chain.

Facile Synthesis of β-Organotellurobutenolides via Electrophilic Tellurolactonization of α-Allenoic Acids

We report a convenient and highly efficient method for the synthesis of beta-organotellurobutenolides by the aryltellurenyl halides-induced electrophilic tellurolactonization of alpha-allenoic acids under mild conditions. The resulting beta-organotellurobutenolides can be utilized as precursors for versatile butenolide derivatives through a substitution reaction with organocuprate reagent or Pd/Cu(I)-catalyzed cross-coupling with terminal alkyne.

Synthesis of 3-pyrrolines, annulated 3-pyrrolines, and pyrroles from alpha-amino allenes

Alpha-amino allenes, readily prepared from reaction of alpha-(N-carbamoyl)alkylcuprates with propargyl substrates followed by N-Boc deprotection, are converted in high yields to pyrrolines with AgNO(3). Palladium-catalyzed cyclization of amino allenes affords either the pyrroline or the pyrrole depending on reaction conditions and provides for introduction of an aryl substituent at the C-3 position of the pyrroline or pyrrole. Enantioenriched pyrrolines are readily prepared from scalemic propargyl alcohols. [reaction: see text]