Application of heterocyclic aldehydes as components in Ugi-Smiles couplings

New tandem Ugi/intramolecular Diels-Alder reaction based on vinylfuran and 1,3-butadienylfuran derivatives

A new tandem sequence involving the Ugi reaction and Diels-Alder [4 + 2] cycloaddition based on vinylfuran and 1,3-butadienylfuran derivatives was designed and studied. It was found that in the case of 3-(furan-2-yl)acrylaldehyde, a one-pot Ugi reaction and intramolecular Diels-Alder vinylarene (IMDAV) reaction leads to the formation of the insufficiently studied furo[2,3-f]isoindole derivatives. Ugi adducts formed from (E)-3-(furan-2-yl)acrylaldehyde, maleic acid monoanilide, isonitrile, and an amine spontaneously underwent the IMDAV reaction with a high level of stereoselectivity, leading to single pairs of enantiomers of 4,4a,5,6,7,7a-hexahydro-3aH-furo[2,3-f]isoindole core in excellent yields. Under the same conditions, the (2E,4E)-5-(furan-2-yl)penta-2,4-dienal gives an Ugi adduct that undergoes the IMDA reaction without involving the furan core. The cycloaddition leads to the formation of 2,3,3a,4,5,7a-hexahydro-1H-isoindoles in high yields. The studied tandem Ugi and intramolecular Diels-Alder reactions allow high substituent variation in the named isoindoles.

Ultrasound-assisted diastereoselective green synthesis of spiro-fused-γ-lactams functionalized with an amide bond heterocyclic bioisostere via the Ugi azide/domino process coupled strategy

A series of linked-type 1,5-disubstituted tetrazoles (1,5-DS-Ts) were synthesised via an isocyanide-based multicomponent reaction (IMCR) and used as synthetic platforms to access bound-type polyheterocycles containing an epoxyisoindol-1(6H)-one scaffold under green conditions. This rapid sonochemical synthetic strategy includes a double domino process using an orthogonal heterocyclic input in the Ugi-azide (UA) reaction. DFT calculations and NBO analysis were performed to understand the pseudopericyclic reaction involved in the 1,5-electrocyclization of the UA mechanism.