Synthesis of Polysubstituted Isoquinolines and Related Fused Pyridines from Alkenyl Boronic Esters via a Copper-Catalyzed Azidation/Aza-Wittig Condensation Sequence.

An efficient and straightforward synthesis of isoquinolines is reported from internal alkenyl boronic esters, easily prepared from the corresponding 1,2-bis(boronates), via a sequential copper-catalyzed azidation/aza-Wittig condensation. This synthetic method has been used to synthesize quinisocaine, a topical anesthetic used for the treatment of pain and pruritus, and further extended to thieno[2,3-c]pyridines by using 2-thiophenecarboxaldehyde as coupling partner in the first step.

Synthesis of 1-Amino-1H-Indenes via a Sequential Suzuki-Miyaura Coupling/Petasis Condensation Sequence.

An efficient and straightforward synthesis of 1-amino-1H-indenes is reported from 1,2-bis(boronates) via a sequential Suzuki-Miyaura coupling/Petasis cyclization reaction. Starting from the same monoboronic ester intermediates, an intermolecular version of this approach also afforded (Z)-α,ß-unsaturated amino esters in moderate to good yields.

Regio- and stereocontrolled access to γ-boronated unsaturated amino esters and derivatives from (Z)-alkenyl 1,2-bis(boronates).

The Borono-Mannich reaction of (Z)-1-alkene-1,2-diboronic esters proceeded regioselectively at the terminal C-B bond to afford (E)-γ-boronated unsaturated amino esters in good yields. These compounds were then subjected to Suzuki couplings for the creation of diversely substituted olefinic amino acid systems. Several other functional transformations were also carried out to illustrate the synthetic utility of the Petasis products.