Ca(II)-Mediated Regioselective One-pot Sequential Annulation of Acyclic compounds to Polycyclic Fluorenopyrans

Benzannulation Reactions: A Case for Perspective Change From Arene Decoration to Arene Construction

Benzannulation reactions involve construction of a benzene ring from acyclic precursors. This class of reactions offer a versatile and often superior alternative to aromatic substitution for construction of substituted arenes. Selected pioneering and recent reports of various benzannulation reactions are categorised and discussed in this review.

DFT Analysis into the Calcium(II)-Catalyzed Coupling of Alcohols With Vinylboronic Acids: Cooperativity of Two Different Lewis Acids and Counterion Effects

The mechanism of the calcium-catalyzed coupling of alcohols with vinylboronic acids has been analyzed by means of density functional theory computations. This study reveals that the calcium and boron Lewis acids associate to form a superelectrophile able to promote a pericyclic group transfer reaction with allyl alcohols. With other alcohols, the two Lewis acids act synergistically to activate the OH functionality and trigger a S_Ni reaction pathway. These two mechanisms are affected by the nature of the counterions, which has been rationalized by electronic and steric factors.

Calcium-catalyzed formal [3 + 2] annulation of C,N-diacyliminium ions with nucleophilic phenols: a diversity oriented synthesis of 3-aminofurans

We have developed a one-pot, three-component, and solvent-free reaction for the synthesis of 3-aminofurans using a calcium catalyst. In this cascade reaction, the key intermediate, C,N-diacyliminium ion, is formed in situ from glyoxal and lactam, which further reacted with phenolic nucleophiles to form furan derivatives in good yields with broad substrate diversity. We also present here the preliminary photophysical studies of selected compounds.

Recent advances in alkaline earth metal-enabled syntheses of heterocyclic compounds

This review summarizes recent progress in alkaline earth metal enabled syntheses of heterocyclic compounds.

Synthesis of blue emissive functionalized 9,9-disubstituted fluorene derivatives via BF3·OEt2 mediated reaction of co-planar 9-(phenylethynyl)-9H-fluoren-9-ols with isatin imines

A BF₃·Et₂O mediated reaction of co-planar 9-(phenylethynyl)-9H-fluoren-9-ol with various isatin imines afforded title compounds in excellent yield. The products showed luminescence in the blue region with large Stokes shift.

Calcium-Catalyzed Stereoselective Tandem [4+2] and [3+2] Annulation Reaction for the Synthesis of Dihydropyrrolo[1,2-a]quinolines

Calcium-catalyzed highly facile one-pot, A⁴ annulation of aldehyde, amine, alkene, and alkyne to form fused 4,5-dihydropyrrolo[1,2-a]quinolines with exclusive syn diastereoselectivity is reported. This selectivity arises from an inverse electron demand [4+2] aza-Diels-Alder cycloaddition, and the adduct further undergoes a formal [3+2] cyclization with activated alkynes. This diversity-oriented protocol is highly general and furnishes the dihydropyrrolo[1,2-a]quinoline derivatives with a broad substrate scope in good to excellent yields.