Access to Fused Pyrroles from Cyclic 1,3-Dienyl Boronic Esters and Arylnitroso Compounds

Abstract

Complimentary to classical hydroboration and boron-Wittig reactions, a new, efficient access to cyclic 1,3-dienyl boronic esters has been developed via diene or triene metathesis. Subsequently, fused pyrroles were synthesized with a broad substrate scope from the reaction of cyclic 1,3-dienyl boronic esters with arylnitroso compounds using a one-pot hetero-Diels−Alder/ring contraction sequence.

The transition metal-catalysed hydroboration reaction

“…Regioselectivity for the cis-hydroboration of the terminal alkyne in conjugated enynes has been found to be excellent with a catalyst system based on Schwartz's reagent, triethylamine, and pinacolborane (Scheme 42). 226,227 Selectivity for the linear borylated product is reduced somewhat using a NiCl 2 /dppe catalyst system. 228 trans-Hydroboration reactions have also been demonstrated using catecholborane and a palladium(0)/1,4-azoborine-based phosphine ligand system.…”

Application of Olefin Metathesis in the Synthesis of Carbo- and Heteroaromatic Compounds—Recent Advances

“…Whiting and Carboni showed a different approach to the synthesis of pyrroles [ 38 ]. In the first step, they performed ring-closing enyne metathesis (RCEM), followed by cross-metathesis (CM) with vinylboronic esters to form a large spectrum of cyclic dienyl boronic esters ( Scheme 16 ).…”

Brønsted-Acid-Catalyzed (3+2)-Cycloannulation of In-Situ-Generated 3-Methide-3H-pyrroles: Asymmetric Synthesis of Cyclopenta[b]pyrroles

“…Therefore, a lot of synthetic effort has been directed to establish this structural motif. − Noteworthy examples include Paal–Knorr-related dehydrations, ,, a Pt-catalyzed cascade cyclization/ring expansion of propargylic aziridines, an Ir-catalyzed dehydrogenative condensation, or Nazarov cyclizations toward cyclopentenone-fused pyrroles. However, despite the interesting biological and medicinal properties, little effort has been devoted toward a general asymmetric synthesis of cyclopenta­[ b ]­pyrroles.…”