Lewis-Acid-Catalyzed Tandem Cyclization by Ring Expansion of Tertiary Cycloalkanols with Propargyl Alcohols

A new method for the efficient synthesis of hexahydro-1H-fluorene and octahydrobenzo[a]azulene derivatives through a ring-expansion strategy is reported. With an appropriate combination of thulium(III) trifluoromethanesulfonate and 13X molecular sieves, a range of unsaturated polycyclic compounds were obtained in good yields. Mechanism studies reveal that the reaction is more likely to undergo Meyer-Schuster rearrangement, ring expansion, and Friedel-Crafts-type pathways, which provide a conceptually different strategy for the ring opening of tertiary cycloalkanols.

Copper-Catalyzed Cycloisomerization of Unactivated Allene-Tethered O-Propargyl Oximes: A Domino Reaction Sequence toward the Synthesis of Hexahydropyrrolo[3,4-b]azepin-5(4H)-ones

A novel copper-catalyzed cycloisomerization of unactivated allene-tethered O-propargyl oximes has been developed for the synthesis of hexahydropyrrolo[3,4-b]azepin-5(4H)-ones. This one-pot domino reaction proceeds via a [2,3]-sigmatropic rearrangement, a [3 + 2] cycloaddition, and another [3,3]-sigmatropic rearrangement. The methodology offers a practical and straightforward route for the rapid assembly of both ring components of the fused bicyclic motifs from acyclic precursors by simultaneously forming four new bonds (a C═O, a C═N, and two C-C bonds) in a single step.

Rhodium-catalyzed annulation of pyrrole substituted BODIPYs with alkynes to access π-extended polycyclic heteroaromatic molecules and NIR absorption

A series of π-extended BODIPY derivatives fused with an indolizine scaffold were prepared smoothly via rhodium-catalyzed C–H functionalization/annulation. These fluorophores show significantly red-shifted absorption, reaching to the near infrared (NIR) region.

Two- and three-dimensional β,β′-N-heterocycle fused porphyrins: concise construction, singlet oxygen production and electro-catalytic hydrogen evolution reaction

A series of 2D and 3D porphyrins fused with N-heterocycles were prepared by palladium-catalyzed. Photophysical and electrochemical properties, 1O2 production and electrocatalytic HER behaviours of the representative porphyrins were investigated.

Recent Advances in Cycloaddition Reactions with Alkynes to Construct Heterocycles

Heterocyclic compounds, especially N-heterocycles and O-heterocycles, are prominent structural motifs present in numerous natural products and medically and/or economically important compounds. This review aims to describe the development of transition-metal-catalyzed cycloaddition reactions of functionalized m-atom partners with alkynes to access a wide range of five-, six-, and seven-membered heterocycles, that is functionalized N-heterocycles and O-heterocycles such as azepines, isoquinolines, isocoumarins, spiroheterocycles, indoles, furans, and pyrroles, in a selectively controlled manner with an emphasis on scope and limitations and with a discussion of the mechanisms.

1 Introduction

2 Intermolecular Cycloaddition To Construct Azepine Derivatives

2.1 [5+2] Cycloaddition

2.2 [3+2+2] Cycloaddition

2.3 [3+2]/[5+2] Cycloaddition

3 Intermolecular [4+2] Cycloaddition To Construct Isoquinolines or Isocoumarins

4 Intermolecular [3+2] Cycloaddition To Construct Spirohetero­cyclic Compounds, Indoles, Furans, and Pyrroles

5 Summary and Outlook