Bifunctional Organo/Metal Cooperatively Catalyzed [3 + 2] Annulation of <i>para</i>-Quinone Methides with Vinylcyclopropanes: Approach to Spiro[4.5]deca-6,9-diene-8-ones

A novel [3 + 2] annulation between <i>para</i>-quinone methides and vinylcyclopropanes for the synthesis of spiro[4.5]­deca-6,9-diene-8-ones has been described. The palladium and phosphine–thiourea cooperative catalysis system played an important role in high yields and diastereoselectivities. The reaction exhibited good functional group tolerance and scalability

Bifunctional Organo/Metal Cooperatively Catalyzed [3 + 2] Annulation of <i>para</i>-Quinone Methides with Vinylcyclopropanes: Approach to Spiro[4.5]deca-6,9-diene-8-ones

A novel [3 + 2] annulation between <i>para</i>-quinone methides and vinylcyclopropanes for the synthesis of spiro[4.5]­deca-6,9-diene-8-ones has been described. The palladium and phosphine–thiourea cooperative catalysis system played an important role in high yields and diastereoselectivities. The reaction exhibited good functional group tolerance and scalability

Rhodium-Catalyzed Hydroacylation of <i>para</i>-Quinone Methides with Salicylaldehydes: An Approach to α,α-Diaryl-2-Hydroxy Acetophenones

A rhodium-catalyzed hydroacylation of <i>para</i>-quinone methides (<i>p</i>-QMs) with salicylaldehydes has been disclosed. This method allows for the construction of α,α-diaryl-2-hydroxy acetophenones through tandem C–H activation/C–C bond formation/aromatization process. Moreover, this unprecedented hydroacylation of trisubstituted alkenes exhibits good yields with broad functional group tolerance as well as gram-scale capacity

Organocatalyzed [3 + 2] Annulation of Cyclopropenones and β‑Ketoesters: An Approach to Substituted Butenolides with a Quaternary Center

An unprecedented organocatalyzed [3 + 2] annulation of cyclopropenones and β-ketoesters has been developed. This reaction provides a direct approach to highly substituted butenolides with a quaternary center in moderate to good yields. The preliminary mechanism study verified that the enol intermediate is crucial to the reaction outcome and the intermolecular esterification and intramolecular Michael addition process were involved

Synthesis of Spiropentadiene Pyrazolones by Rh(III)-Catalyzed Formal sp³ C–H Activation/Annulation

A Rh-catalyzed enol-directed formal sp³ C–H activation/annulation of α-arylidene pyrazolones with alkynes has been developed. This reaction provides a convenient route to synthesize spiropentadiene pyrazolones in good to excellent yields at room temperature, exhibiting good functional group tolerance, gram scalability, and high regioselectivity. Of note, the α-arylidene pyrazolone was introduced as a novel C3 synthon in C–H activation/annulation

Rh(III)-Catalyzed Cascade Annulation/C–H Activation of <i>o</i>‑Ethynylanilines with Diazo Compounds: One-Pot Synthesis of Benzo[<i>a</i>]carbazoles via 1,4-Rhodium Migration

A Rh­(III)-catalyzed cascade annulation/C–H activation of <i>o</i>-ethynylanilines with diazo compounds has been developed. This concise method allows for the rapid formation of a number of benzo­[<i>a</i>]­carbazoles in high yields, exhibiting good functional group tolerance and scalability. The key to the success of this approach involves one C–N bond and two C–C bond formation, and an aryl-to-aryl 1,4-rhodium migration

Organocatalyzed Asymmetric 1,6-Conjugate Addition of <i>para</i>-Quinone Methides with Dicyanoolefins

A chiral thiourea catalyzed asymmetric 1,6-conjugate addition of <i>para</i>-quinone methides with dicyanoolefins has been developed. The reaction provided an efficient approach to the synthesis of chiral diarylmethine skeletons in good yields (up to 99% yield) with high diastereo- and enantioselectivity (>20:1 dr and up to 99.5:0.5 er), also on a gram scale. The preliminary mechanistic study showed that the remote stereocontrol was achieved through intermolecular hydrogen-bond interaction between the chiral thiourea catalyst and the <i>para</i>-quinone methides directly for the first time

[3 + 3] Cycloaddition of Azides with in Situ Formed Azaoxyallyl Cations To Synthesize 1,2,3,4-Tetrazines

A formal [3 + 3] cycloaddition reaction between azides and in situ formed azaoxyallyl cations has been realized. This reaction provided an efficient and practical pathway to synthesize 1,2,3,4-tetrazines in good yields under mild conditions. Biologically active molecules could also be well compatible, highlighting the potential value of this reaction

Rh(III)-Catalyzed Cascade Annulation/C–H Activation of <i>o</i>‑Ethynylanilines with Diazo Compounds: One-Pot Synthesis of Benzo[<i>a</i>]carbazoles via 1,4-Rhodium Migration

A Rh­(III)-catalyzed cascade annulation/C–H activation of <i>o</i>-ethynylanilines with diazo compounds has been developed. This concise method allows for the rapid formation of a number of benzo­[<i>a</i>]­carbazoles in high yields, exhibiting good functional group tolerance and scalability. The key to the success of this approach involves one C–N bond and two C–C bond formation, and an aryl-to-aryl 1,4-rhodium migration