Regio- and diastereoselective synthesis of diverse spirocyclic indenes by cyclization with indene-dienes as two carbon building blocks.

We report a base-promoted cyclization with indene-dienes as two carbon building blocks toward diverse spirocyclic indene scaffolds including hexacyclic spiroindenes bearing benzo pyran motifs and pentacyclic spiroindenes containing oxindole units in high yields with excellent diastereoselectivities.

A regioselective [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones with functional olefins to access indanone-fused 2D/3D skeletons.

The regioselective [3 + 2] cycloaddition reaction of 2-benzylidene-1-indenones with functional olefins was established with DABCO as a base under mild conditions. Using this approach, a series of diversely substituted indanone-fused cyclopentane polycycles with highly crowded multiple substituents were synthesized in high yields.

Construction of an Axially Chiral Fluorene Nitrile-Based Framework via Benzannulation of Indene Diene with Benzoylacetonitrile.

The methodology for the synthesis of fluorene-based atropisomers was developed via the strategy of aromatic ring formation. By this strategy, an efficient benzannulation of indene-based diene with benzoylacetonitrile divergently promoted by DABCO and a chiral organocatalyst was established, and various atropisomeric fluorene-based skeletons were generated in good yields, which not only provide a new strategy for the construction of atropisomeric biaryls but also offer a new member to the atropisomeric family.

Phosphine-Catalyzed Synthesis of 3-Allyl-4-pyrones by the Tandem Reaction of Diynones and Allylic Alcohols.

A simple and effective tandem reaction of diynones and allylic alcohols was developed to afford functionalized 3-allyl-4-pyrones in moderate to excellent yields. This protocol underwent a Michael addition─Claisen rearrangement─O-cyclization process, which exhibited broad substrate tolerance, high regioselectivity, and atom economy under a metal-free condition. Moreover, functional transformation of the products was also further studied.

Divergent Metal-Free [4 + 2] Cascade Reaction of 1-Indanylidenemalononitrile with 3-Benzylidenebenzofuran-2(3H)-one: Access to Spiro-dihydrofluorene-benzofuranone and Axially Chiral Fluorenylamine-phenol Derivatives.

An efficient cascade reaction of 1-indanylidenemalononitrile with 3-benzylidenebenzofuran-2(3H)-one divergently promoted by DABCO or chiral organocatalyst was developed under mild reaction conditions, and various spiro-dihydrofluorene-benzofuranones were produced in gratifying results, respectively. It is worth noting that both the spiro and axially chiral products can be obtained by tuning the reaction conditions. The mechanism of the transformation was also studied by quantum chemical calculations.

Catalyst- and Additive-Free Annulation of Ynediones and (Iso)Quinoline N-Oxides: An Approach to Synthesis of Pyrrolo[2,1-a]Isoquinolines and Pyrrolo[1,2-a]Quinolines.

A simple and effective annulation of ynediones and (iso)quinoline N-oxides was developed to afford various functionalized pyrrolo[2,1-a]isoquinolines and pyrrolo[1,2-a]quinolines in moderate to excellent yields. This protocol underwent a tandem [3 + 2] cycloaddition/ring-opening/N-nucleophilic addition, which exhibited high regioselectivity, broad substrate tolerance, and atom economy under catalyst-, additive-free, and air conditions. Moreover, indolizine was also successfully prepared using pyridine N-oxide.

Correction to "Monitoring the Hierarchical Evolution from a Double-Stranded Helix to a Well-Defined Microscopic Morphology Based on a Turbine-like Aromatic Molecule".

[This corrects the article DOI: 10.1021/acsomega.0c01443.].

Correction: Metal-free [3+3] benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates: direct access to functionalized fluorene and fluorenone derivatives.

Correction for 'Metal-free [3+3] benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates: direct access to functionalized fluorene and fluorenone derivatives' by Ya-Sa Xie et al., Chem. Commun., 2020, 56, 1948-1951, DOI: 10.1039/D0CC00143K.

Monitoring the Hierarchical Evolution from a Double-Stranded Helix to a Well-Defined Microscopic Morphology Based on a Turbine-like Aromatic Molecule.

1H-Indazolo[1,2-b]phthalazine-5,10-dione IPDD with an approximate turbine-like spatial structure, primary assembled double-stranded helices at the first level, was predicted by quantum chemical calculations and confirmed by atomic force microscopy. The higher-dimensional hierarchical architectures including fibrils, helical fibers, spherical shells, and porous prismatic structures were observed in sequence by the scanning electron microscopy technique. The final porous prismatic structures sensitive to NH3 vapors have the potential to be applied in gas sensing and absorbing materials.

Metal-free [3+3] benzannulation of 1-indanylidene-malononitrile with Morita-Baylis-Hillman carbonates: direct access to functionalized fluorene and fluorenone derivatives.

An efficient [3+3] benzannulation of Morita-Baylis-Hillman carbonates with 1-indanylidenemalononitrile was achieved under metal-free reaction conditions selectively delivering a wide range of functional multi-substituted fluorene or fluorenone compounds in high yields, respectively (up to 86% yield). Moreover, experiments and quantum chemical calculations were also performed to study the mechanism of the transformation.

Controllable synthesis of 3-iodo-2H-quinolizin-2-ones and 1,3-diiodo-2H-quinolizin-2-ones via electrophilic cyclization of azacyclic ynones.

An effective electrophilic annulation reaction of azacyclic ynones was reported, divergently affording various functionalized 3-iodo-2H-quinolizin-2-ones and 1,3-diiodo-2H-quinolizin-2-ones in moderate to excellent yields with different iodide reagents. This reaction shows high regioselectivity and broad substrate scope under metal-free, room temperature conditions in air. In addition, the products with highly active C-I bonds have an opportunity for further functionalization.

Base-Controlled Divergent Synthesis of 5-Cyanobenzoxepines and Benzofuro[2,3-b]pyridines from 2-Bromophenylacetonitriles and Ynones.

An effective base-controlled divergent annulation reaction of 2-bromophenylacetonitriles and ynones has been developed. Various functionalized 5-cyanobenzoxepines and benzofuro[2,3-b]pyridines were obtained with a broad substrate scope and high regioselectivity in moderate to excellent yield. Of importance, an unexpected O-rearrangement reaction to access benzofuro[2,3-b]pyridines was observed using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as the base, and the possible mechanism was supported by 18O-labeled experiments. In addition, the gram-scale synthesis and further transformation of the product were studied.

Synthesis of 1-Cyano-3-acylnaphthalenes via Formal [4+2] Benzannulation of 2-(2-Alkynylphenyl)acetonitriles and Alkynones.

Effective transition-metal-free formal [4+2] benzannulation for the preparation of 1-cyano-3-acylnaphthalenes from 2-(2-alkynylphenyl)acetonitriles and alkynones through sequential C-C bond coupling has been developed. This protocol is characterized by mild conditions, excellent functional group tolerance, complete regioselectivity, and atom economy. The plausible mechanism, gram-scale synthesis, and further transformations of the product were studied.

Construction of quaternary stereocenters: asymmetric α-amination of branched aldehydes catalyzed by monoimide substituted cyclohexane-1,2-diamines.

A highly efficient enantioselective α-amination of branched aldehydes catalyzed by chiral imide monosubstituted 1,2-diamine derivatives was reported to afford the quaternary stereogenic centers in excellent yields (up to 99%) and enantioselectivities (up to 97% ee). Chirality 25:668-672, 2013. © 2013 Wiley Periodicals, Inc.

Enantioselective α-amination of branched aldehydes promoted by simple chiral primary amino acids.

A series of simple chiral primary amino acids were first successfully applied to promote the enantioselective α-amination of branched aldehydes with azadicarboxylates and the desired adducts bearing quaternary stereogenic centers were obtained in excellent yields (up to 99%) and enantioselectivities (up to 97% ee).

Effective construction of quaternary stereocenters by highly enantioselective α-amination of branched aldehydes.

A highly efficient enantioselective α-amination of branched aldehydes with azadicarboxylates promoted by chiral proline-derived amide thiourea bifunctional catalysts was developed for the first time, affording the adducts bearing quaternary stereogenic centers with excellent yields (up to 99%) and enantioselectivities (up to 97% ee).