α-Regioselective Asymmetric [3 + 2] Annulations of Morita–Baylis–Hillman Carbonates with Cyclic 1-Azadienes and Mechanism Elucidation

COAP-Pd Catalyzed Asymmetric Formal [3+2] Cycloaddition for Optically Active Multistereogenic Spiro Cyclopentane-Indandiones Bearing Cyclic N-Sulfonyl Ketimine Skeletons

We reported a chiral oxamide-phosphine ligand (COAP-Ph)-Pd-catalyzed asymmetric [3+2] cycloaddition reaction between vinyl cyclopropane compounds derived from 1,3-indanedione and 2-vinylcyclopropane-1,1-dicarboxylates with cyclic sulfonyl 1-azadienes. The corresponding reactions provided a series of enantiomerically active spiro cyclopentane-indandione and cyclopentane structures bearing three consecutive stereogenic centers in good yields with good diastereo- and enantioselectivity. The COAP-Pd complex serves not only to promote generation of chiral π-allyl-palladium intermediates and induce the asymmetry of the reaction, but also depress the background reaction.

Substrate-Controlled Diversity-Oriented Synthesis of Novel Polycyclic Frameworks via [4 + 2] and [3 + 2] Annulations of Ninhydrin-Derived MBH Adducts with 3,4-Dihydroisoquinolines

Substrate-controlled diversity-oriented synthesis of polycyclic frameworks via [4 + 2] and [3 + 2] annulations between ninhydrin-derived Morita-Baylis-Hillman (MBH) adducts and 3,4-dihydroisoquinolines under similar reaction conditions have been developed. The reaction provides diversity-oriented synthesis of a series of novel and structurally complex spiro multi heterocyclic skeletons in good yields (up to 87% and 90%, respectively) with excellent diastereoselectivities (up to >25:1 dr). In particular, the switchable [4 + 2] and [3 + 2] annulation reactions are controlled by tuning the hydroxyl protecting group on the ninhydrin-derived MBH adduct to deliver structural diverse spiro[indene-2,2'-[1,3]oxazino[2,3-a]isoquinoline] and spiro[indene-2,1'-pyrrolo[2,1-a]isoquinoline], respectively. Furthermore, the relative configuration and chemical structure of two kinds of cycloadducts were confirmed through X-ray diffraction analysis.

DMAP-Catalyzed [4+3] Spiroannulation of Pyrazolone-Derived Morita-Baylis-Hillman Carbonates with N-(o-Chloromethyl)aryl Amides to Forge Spiro[pyrazolone-azepine] Scaffolds

A novel DMAP-catalyzed [4+3] spiroannulation of pyrazolone-derived Morita-Baylis-Hillman carbonates with N-(o-chloromethyl)aryl amides was developed. This reaction led to the assembly of medicinally relevant pyrazolone and azepine nuclei into a structurally new spirocyclic scaffold, and a diverse array of spiro[pyrazolone-azepine] products were afforded in good to excellent yields (up to 93%) with a wide substrate scope (23 examples) under mild conditions. Moreover, a gram-scale reaction and product transformations were conducted, which further increased the diversity of products.

Organocatalyzed Enantioselective Aza-Morita-Baylis-Hillman Reaction of Cyclic Ketimine with α,β-Unsaturated γ-Butyrolactam

The enantioselective aza-MBH reaction is an efficient strategy for constructing novel carbon-carbon bonds, providing access to multitudinous chiral densely functionalized MBH products. However, the enantioselective aza-MBH reaction of cyclic-ketimines that would generate a versatile synthon is still missing and challenging. Herein, we developed a challenging direct organocatalytic asymmetric aza-MBH reaction involving cyclic ketimines attached to a neutral functional group. Moreover, the α,β-unsaturated γ-butyrolactam was utilized as a rare nucleophile alkene in this work. The reactions provide enantiomerically enriched 2-alkenyl-2-phenyl-1,2-dihydro-3H-indol-3-ones, bearing with a tetra-substituted stereogenic center. Moreover, this reaction features high α-selectivities, high enantioselectivities (up to 99% ee), and good yields (up to 80%).

Asymmetric α-Regioselective [3 + 2] Annulation of Morita-Baylis-Hillman Carbonates: Construction of Three Contiguous Stereocenters with Vicinal Quaternary Carbon Centers

Asymmetric α-regioselective annulation of MBH carbonates with 4-arylmethylisoxazol-5-ones has been developed to afford spirocyclic oxindole derivatives containing three contiguous stereogenic centers and vicinal all-carbon quaternary chiral centers. This reaction exhibits a broad substrate scope and excellent functional group tolerance. Excellent yields with high diastereo- and enantioselectivities were obtained in this efficient organocatalytic reaction.

Substrate-Controlled Regioselectivity Switchable [3 + 2] Annulations To Access Spirooxindole Skeletons

The additive-free [3 + 2] annulation from isatins, amino acids with 2-styrylbenzoxazoles, was described, providing a series of functional and structurally complex 3,3'-pyrrolidinyl-spirooxindole derivatives containing four contiguous and two quaternary stereogenic centers in high yields (up to 95%) and excellent diastereoselectivities (up to >25:1 dr). Interestingly, the reaction exhibits switchable regioselectivity depending on the substrate of amino acids. With proline or thioproline as the substrate, the reaction afforded α-regioselective spirooxindole skeletons. In contrast, when piperidine acid is the substrate, the reaction provided γ-regioselective spirooxindole skeletons.

Organocatalytic Regio- and Enantioselective [3 + 2]-Annulations of Ninhydrin-Derived Morita-Baylis-Hillman Carbonates with 3-Methyleneoxindoles

A type of Morita-Baylis-Hillman (MBH) carbonates has been developed from ninhydrin. These MBH carbonates have been successfully employed as 3C-synthons in the organocatalytic asymmetric [3 + 2]-annulations of the isatin-derived electron-deficient olefins, affording structurally diverse spirooxindoles in high yield with excellent stereoselectivity. In particular, the regioselectivity of MBH carbonates was controlled by the reaction partner, 3-methyleneoxindoles with carbonyl groups (R = ArCO), affording β-selective products and 3-methyleneoxindoles with ester groups (R = CO₂Me) furnishing γ-selective products. The representative scale-up reactions and transformation of product were examined. The reaction mechanism was expounded by control experiments.

Dinuclear zinc catalyzed asymmetric [3 + 2] spiroannulation for the synthesis of diverse bispirocyclic saccharines

A highly atom-economical and novel enantioselective [3 + 2] spiroannulation reaction of saccharine-derived cyclic 1-azadienes with α-hydroxy-1-indanones has been developed.

Asymmetric [3 + 2] spiroannulation of pyrazolone-derived Morita–Baylis–Hillman carbonates with alkynyl ketones: facile access to spiro[cyclopentadiene-pyrazolone] scaffolds

A tertiary amine-catalyzed asymmetric [3 + 2] spiroannulation reaction of pyrazolone-derived Morita–Baylis–Hillman carbonates with alkynyl ketones was achieved under mild conditions. This protocol offers a facile approach to chiral spiro[cyclopentadiene-pyrazolone]...

Organocatalytic asymmetric synthesis of multifunctionalized α-carboline-spirooxindole hybrids that suppressed proliferation in colorectal cancer cells

An asymmetric organocatalytic cascade reaction has been reported for the rapid assembly of multifunctionalized α-carboline-spirooxindole hybrids, which suppressed proliferation in colorectal cancer cells.

Formal (3 + 1 + 1) Carboannulation of Morita-Baylis-Hillman Carbonates with Pyridinium Ylides: Access to Spiro-Cyclopentadiene Oxindoles

An efficient formal (3 + 1 + 1) carboannulation strategy of Morita-Baylis-Hillman (MBH) carbonates with pyridinium ylides was developed for constructing diversely functionalized spiro-cyclopentadiene oxindoles. The reaction initiates with an S_N2' olefination of MBH carbonates with pyridinium ylides. The in situ generated dienes then engage in a challenging (4 + 1) ylide carboannulation, which has been rarely reported before. The reaction features broad substrate scope as well as high chemo- and regioselectivity. (3 + 1 + 1) carboannulation products could be easily transformed into interesting spiro-cyclopenta[c]furan oxindoles.

Construction of cyclopentane-fused coumarins via DBU-catalyzed [3+2] cycloaddition of 3-homoacyl coumarins with cyclic 1-azadienes

The metal-free DBU catalyzed [3+2] cycloaddition of 3-homoacyl coumarins with cyclic 1-azadienes proceeded smoothly to furnish the corresponding highly functionalized cyclopentane-fused coumarins with excellent diastereoselectivity and complete chemoselectivity and in good yields under mild conditions.

A metal-free DBU catalyzed [3+2] cycloaddition of 3-homoacyl coumarins with cyclic 1-azadienes has been developed for the synthesis of cyclopentane-fused coumarins with excellent diastereoselectivity and complete chemoselectivity.

Organocatalytic asymmetric formal [3 + 2] cycloaddition reaction of isocyanoacetates with saccharin-derived 1-azadienes

An efficient organocatalytic diastereo- and enantioselective formal [3 + 2] cycloaddition reaction of α-isocyanoacetates with saccharin-derived 1-azadienes catalyzed by a dihydroquinine derived squaramide catalyst has been investigated, and it furnished the corresponding directly linked benzo[d]isothiazole 1,1-dioxide-dihydropyrroles with two adjacent tertiary-quaternary stereocenters in high yields (up to 98%), with moderate to excellent stereoselectivities (up to >20 : 1 dr and 97% ee) under mild conditions.

Design and organocatalytic synthesis of spirooxindole–cyclopentene–isoxazole hybrids as novel MDM2–p53 inhibitors

An organocatalytic 1,6-cycloaddition with exclusive α-regioselectivity to synthesize designed spirooxindole–cyclopentene–isoxazole hybrids as novel MDM2–p53 inhibitors.

Reaction condition-dependent divergent synthesis of spirooxindoles and bisoxindoles

DABCO-catalyzed divergent transformations of isatin-derived MBH carbonates leading to either spirocyclopentene oxindoles, spirocyclopentadiene 2-oxindoles or bisoxindoles are described.

Access to highly enantioselective and diastereoselective spirooxindole dihydrofuran fused pyrazolones

Access to highly enantioselective and diastereoselective spirooxindole dihydrofuran fused pyrazolones from MBH-carbonates and pyrazole 4,5-diones.

Enantioselective [3+2] annulation of isatin-derived MBH-carbonates and 3-nitroindoles enabled by a bifunctional DMAP-thiourea

Highly enantioselective [3+2] annulation of isatin-derived MBH-carbonates and 3-nitroindoles was achieved by a chiral DMAP-thiourea bifunctional catalyst.

Synthesis of Substituted Isatins from the MBH Adduct of 1,5,6-Trisubstituted Isatins Using (2,4-Dinitrophenyl)hydrazine and K-10 Clay Explored as Protection-Deprotection Chemistry

An interesting synthetic transformation of protection-deprotection chemistry in an isatin molecule is achieved. Morita-Baylis-Hillman (MBH) adduct formation used as protection of the C-3 position in the isatin molecule is reported. C-C bond cleavage in the MBH adduct of isatin with the help of phenylhydrazine and C=N bond cleavage in the phenylhydrazone derivative of isatin with the help of K10 clay are studied systematically and reported as deprotection.

Asymmetric domino 1,6-addition/annulation reaction of 3-cyano-4-alkenyl-2H-chromen-2-ones with isatin-derived MBH carbonates: enantioselective synthesis of 3,3′-cyclopentenylspirooxindoles bearing 2H-chromen-2-ones

An asymmetric domino 1,6-addition/annulation reaction of 3-cyano-4-alkenyl-2H-chromen-2-ones with isatin-derived MBH carbonates was achieved by using a modified cinchona alkaloid as a catalyst.

Palladium-catalyzed diastereo- and enantioselective formal [3 + 2] cycloaddition of vinyl cyclopropanes with cyclic 1-azadienes

We have developed highly efficient and stereoselective Pd-catalyzed formal [3 + 2] cycloadditions of vinyl cyclopropanes with cyclic 1-azadienes.

Pd-catalyzed [3 + 2] cycloaddition of vinylcyclopropanes with 1-azadienes: synthesis of 4-cyclopentylbenzo[e][1,2,3]oxathiazine 2,2-dioxides

The palladium-catalyzed [3 + 2] cycloaddition of vinylcyclopropanes and 1-azadienes has been developed under mild reaction conditions, giving the multisubstituted cyclopentane derivatives in good to excellent yields with moderate to good diastereoselectivities. The relative configuration of both diastereomers of the products have been determined through X-ray crystallographic diffraction.

An asymmetric Mannich reaction of α-diazocarbonyl compounds and N-sulfonyl cyclic ketimines catalyzed by complexes generated from chiral and achiral phosphines with gold(i)

An unprecedented Lewis acidic gold(i)-complex generated from chiral and achiral phosphines has been developed for the Mannich reaction of α-diazocarbonyl compounds and N-sulfonyl cyclic ketimines. A series of chiral β-amino-α-diazoesters bearing a quaternary stereocenter were obtained in high yields with good enantioselectivities. In addition, the products could be converted to promising bioactive spirosuccinimide. Furthermore, operando IR, NMR and control experiments were carried out to gain insight into the mechanism.

Enantioselective Synthesis of Carbocyclic Nucleosides via Asymmetric [3 + 2] Annulation of α-Purine-Substituted Acrylates with MBH Carbonates

An efficient route to chiral carbocyclic nucleoside analogues containing a quaternary stereocenter and a C═C double bond has been established via a highly enantioselective [3 + 2] annulation of Morita-Baylis-Hillman (MBH) carbonates with α-purine-substituted acrylates. With 20 mol % (S)-SITCP as the catalyst, various chiral carbocyclic nucleoside analogues with a quaternary stereocenter and a C═C double bond were obtained in high yields (up to 92%) with good diastereoselectivities (up to 10:1 dr) and excellent enantioselectivities (up to 96% ee). Furthermore, the corresponding products were subjected to diverse transformations to afford interesting and potentially useful chiral carbocyclic nucleosides.

Multifunctional chiral phosphine-catalyzed [3+2] annulation of Morita-Baylis-Hillman carbonates with cyclopentenones: asymmetric synthesis of 4-oxo-hexahydropentalenes

A multifunctional chiral phosphine-catalyzed enantioselective [3+2] annulation of Morita-Baylis-Hillman carbonates with cyclopentenones provides a direct approach to access functional 4-oxo-1,3a,4,5,6,6a-hexahydropentalene compounds. Moderate to good yields and excellent enantioselectivities (>90% ee) were obtained for a series of substrates under mild reaction conditions.

New development in the enantioselective synthesis of spiro compounds

In this review we summarize the latest developments in the enantioselective synthesis of spirocompounds. The most important organometallic and organocatalytic methodologies are highlighted.

Effective and diastereoselective preparation of dispiro[cyclopent-3′-ene]bisoxindoles via novel [3 + 2] annulation of isoindigos and MBH carbonates

Efficient, one-step preparation of highly steric dispiro[cyclopent-3′-ene]bisoxindoles with two all-carbon quaternary spirocenters and three adjacent cycles in excellent yields and diastereoselectivities under mild conditions.