A [3 + 2]-annulation approach to tetrasubstituted furans from MBH-carbonates of acetylenic aldehydes via sequential substitution/cycloisomerization.

A novel metal-free approach to construct the tetrasubstituted furans from Morita-Baylis-Hillman (MBH)-carbonates of acetylenic aldehydes has been developed. This strategy involves the cascade nucleophilic substitution/5-exo-dig-cycloisomerization of MBH-carbonates with 1,3-dicarbonyl compounds to give uniquely substituted 2-furan-3-yl acrylates. Additionally, the obtained furan adducts open a new entry to naphthofurans through palladium-catalyzed decarboxylative benzannulation.

Sequential allylic substitution/Pauson-Khand reaction: a strategy to bicyclic fused cyclopentenones from MBH-acetates of acetylenic aldehydes.

An efficient approach for the construction of novel bicyclic fused cyclopentenones starting from Morita-Baylis-Hillman (MBH) acetates of acetylenic aldehydes with flexible scaffold diversity has been achieved using a two-step reaction sequence involving allylic substitution and the Pauson-Khand reaction. This strategy provided a facile access to various bicyclic cyclopentenones fused with either a carbocyclic or a heterocyclic ring system in good yield.

Tandem allylic substitution-5-exo-dig-carbocyclization: a [4 + 1]-annulation approach to arylidene cyclopentenes from MBH-acetates of acetylenic aldehydes.

A new entry for the synthesis of functionalized arylidene cyclopentenes under metal-free reaction conditions is disclosed via the base-promoted [4 + 1]-annulation of Morita-Baylis-Hillman acetates of acetylenic aldehydes with active methylene derivatives involving tandem allylic substitution followed by 5-exo-dig-carbocyclization.