Nucleophilic Dearomatizing (DNAr) Reactions of Aromatic C,H-Systems. A Mature Paradigm in Organic Synthesis

Short chemoenzymatic total synthesis of ent-hydromorphone: an oxidative dearomatization/intramolecular [4+2] cycloaddition/amination sequence

A short synthesis of ent-hydromorphone has been achieved in twelve steps from β-bromoethylbenzene. The key transformations involved the enzymatic dihydroxylation of the arene to the corresponding cis-dihydrodiol, Mitsunobu coupling with the ring A fragment, oxidative dearomatization of the C3 phenol, and the subsequent [4+2] cycloaddition to form ring B of the morphinan. The synthesis was completed by intramolecular amination at C9.

Imino exchange reaction in a dearomatization strategy: synthesis of N-acyl diarylamines and phenothiazines from two anilines

A dearomatization strategy of anilines involving an imino exchange as the key step was developed to prepare N-acyl-diarylamines and phenothiazines.

Sterically directed functionalization of the redox-active bis(imino)acenaphthene ligand class: an experimental and theoretical investigation

The synthesis, characterization, and theoretical study of the sterically directed functionalization of the redox-active bis(imino)acenaphthene (BIAN) ligand class has been explored. With dependence on the steric congestion encompassing the N-C-C-N fragment of the Ar-BIAN ligand, functionalization can be directed to proceed either via a radical backbone dearomatization or a nucleophilic imine C-alkylation pathway. The structures of the Ar-BIAN derivatives 14-19 were determined by means of single-crystal X-ray diffraction. The reaction pathways involved in Ar-BIAN functionalization were monitored by means of EPR spectroscopy. The experimental results and observations were examined in conjunction with DFT-D calculations in order to explain the driving forces that direct the pathways leading to Ar-BIAN functionalization.

Organocatalytic asymmetric one-pot sequential conjugate addition/dearomative fluorination: synthesis of chiral fluorinated isoxazol-5(4H)-ones

A facile one-pot sequential conjugate addition/dearomative fluorination transformation of isoxazol-5(4H)-ones with nitroolefins and N-fluorobenzenesulfonimide (NFSI) has been developed. By using a bifunctional chiral tertiary amino-thiourea catalyst, a series of chiral fluorinated isoxazol-5(4H)-ones containing one fluorine-substituted quarternary stereocenter were obtained in high yields with high enantio- and diastereoselectivities. Further transformation of adducts could afford isoxazolidin-5-one derivatives with three contiguous stereocenters.

Unique radical dearomatization and two-electron reduction of a redox-active ligand

The syntheses and characterizations of [Li(4)][(1,2-di-(tert-butyl)-dpp-BIAN)(2)] (7), (1,2-di-(tert-butyl)-dpp-BIAN) (8), and (1-(tert-butyl)-2-OH-dpp-BIAN) (9) are described. Compound 7 was formed via a radical dearomatization, two-electron reduction pathway that was accompanied by vicinal di-tert-butylation of the BIAN ligand backbone. Oxidation of 7 afforded a dearomatized vicinal di-tert-butyl substituted BIAN ligand (8). An analogous dearomatized vicinal tert-butyl-hydroxy substituted BIAN ligand (9) was also isolated in the course of mechanistic studies related to the formation of 7.

Dearomatization strategies in the synthesis of complex natural products

Evolution in the field of the total synthesis of natural products has led to exciting developments over the last decade. Numerous chemoselective and enantioselective methodologies have emerged from total syntheses, resulting in efficient access to many important natural product targets. This Review highlights recent developments concerning dearomatization, a powerful strategy for the total synthesis of architecturally complex natural products wherein planar, aromatic scaffolds are converted to three-dimensional molecular architectures.