Designing and Accurately Developing a [6 + 2] Dipolar Cycloaddition for the Synthesis of Benzodiazocines

Phosphine-Catalyzed (4 + 2) Annulation of Allenoates Bearing Acidic Hydrogen with 1,1-Dicyanoalkenes

α-succinimide-substituted allenoates were employed as phosphine acceptors in phosphine-catalyzed (4 + 2) annulation with 1,1-dicyanoalkenes. They served as C4 synthons in the annulation reaction under mild reaction conditions and produced hexahydroisoindole derivatives in moderate to high yields with good to excellent diastereoselectivities.

Phosphine-Catalyzed (3 + 2) Annulation of γ-Substituted Cinnamic Aldehyde-Derived Morita-Baylis-Hillman Carbonates through Remote Activation

A series of γ-substituted Morita-Baylis-Hillman (MBH) carbonates were synthesized and subjected to phosphine-catalyzed annulations with electrophilic exocyclic alkenes, giving various valuable spirocyclopentenes in moderate to excellent yields with moderate to excellent diastereoselectivities. A large scope of MBH carbonates bearing γ-hydrogen, alkenyl, and alkynyl substituents was well tolerated. The annulation unprecedentedly involves β-, γ-, and δ-carbons of MBH carbonates.

Metal Free Dötz-Type Aminobenzannulation Reaction via 1,1-Dipoles Cross-Coupling

Aryl amines are of constant interest in organic synthesis owing to their ubiquity in natural products, pharmaceuticals, and organic materials. However, C-H amination or pre-functionalization frequently results in uncontrollable site selectivity, over activation and the generation of inseparable mixtures of regio-isomers. Here we present a novel metal free Dötz-type aminobenzannulation reaction that circumvents the selectivity issues inherent in aromatic chemistry, as well as the use of stoichiometric unstable organolithium reagents and toxic chromium complexes. The concept of utilizing readily available isocyanides and Morita-Baylis-Hillman (MBH) carbonates to achieve 1,1-dipoles cross-coupling to construct ketenimine is the key to success, which has been experimentally and computationally verified. The tandem 6π-electrocyclization/aromatization process offers a versatile method for synthesizing functionalized anilines, fused aryl amines and fused heteroaryl amines.

Lewis-Base-Catalyzed Enantioselective Formal [4 + 2] Annulations of Morita-Baylis-Hillman Carbonates: Access to Tetrahydroquinolines Derivatives

The Lewis-base-catalyzed enantioselective formal [4 + 2] annulation reaction of o-acylamino-aryl MBH carbonates and electron-deficient olefins was developed. Tetrahydroquinolines with three sequential stereogenic centers containing a quaternary stereocenter were obtained in high yields with good enantioselectivity.

Divergent Synthesis of Highly Substituted Tetrahydroquinolines and Cyclopentenes via Lewis Base Catalyzed Switchable [4 + 2] and [3 + 2] Annulations of MBH-Carbonates with Activated Olefins

A highly selective and divergent synthesis which enabled access to various complex compounds is highly attractive in organic synthesis and medicinal chemistry. Herein, we developed an effective method for divergent synthesis of highly substituted tetrahydroquinolines via Lewis base catalyzed switchable annulations of Morita-Baylis-Hillman carbonates with activated olefins. The reaction displayed switchable [4 + 2] or [3 + 2] annulations via catalyst or substrate control, providing a diverse range of architectures which contained highly substituted tetrahydroquinolines or cyclopentenes with three contiguous stereocenters bearing a quaternary carbon center in high yields with excellent diastereoselectivities and regioselectivities. Furthermore, synthetic utility of this strategy was further highlighted by gram-scale experiments and simple transformations of the products.

Sythesis of γ-hydroxy-γ-perfluoroalkyl butenolides and exocyclic double bond butanolides via regioselective allylic alkylations of MBH carbonates with 2-perfluoroalkyl-oxazol-5(2H)-ones

Herein, two general one-pot two-step methods for the preparation of γ-hydroxyl-γ-perfluoromethyl butenolides and γ- hydroxyl-γ-perfluoromethyl exocyclic double bond butanolides from Morita−Baylis−Hillman (MBH) carbonates with 2-perfluoroalkyl-oxazol-5(2H)-ones have been reported for the...

Catalyst-Controlled Divergent Intramolecular Cyclizations of Morita-Baylis-Hillman Carbonates

Unprecedented catalyst-controlled divergent cyclizations of Morita-Baylis-Hillman carbonates have been established using either Cs₂CO₃ or quinuclidine as the catalyst. 1,2-Dihydroquinolines and 4H-3,1-benzoxazines were efficiently synthesized via S_N2' and S_N2'-S_N2' processes, respectively. DFT calculations have led to a deeper understanding of these reaction modes and chemoselectivity.