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A regio- and stereoselective cycloaddition of 6,6-spiroepoxycyclohexa-2,4-dienones with indene leading to benzo-annulated spiroepoxytricyclo[5.2.2.0(2,6)]undec-10-en-9-ones has been described. Manipulation of the oxirane ring in adducts furnished benzotricyclo[5.2.2.0(2,6)]undecanes endowed with a beta,gamma-enone chromophore. Photochemical reaction of beta,gamma-enones upon direct irradiation (1S) gave annulated bicyclo [4.2.0]octenones as a consequence of a stereoselective 1,3-acyl shift. Triplet excitation of chromophoric systems led to oxa-di-pi-methane reaction and gave pentacyclic products which upon cleavage of cyclopropane ring furnished benzoannulated triquinanes. An interesting effect of substituent on the photoreaction has also been observed. (C) 2018 Elsevier Ltd. All rights reserved.

A stereoselective approach to tricyclic core of yaoshanenolides from simple aromatic precursor is described. Cycloaddition of highly reactive spiroepoxycyclohexa-2,4-dienone, stereoselective Grignard reaction, alkylation, and ring-closing metathesis reaction are the key features of our approach. (C) 2014 Elsevier Ltd. All rights reserved.

The efficient generation of complex molecular architectures from simple precursors is one of the most important aspects in the design and development of synthetic methodologies. The chemistry of reactive species generated by the oxidative dearomatization of phenols, such as o -quinone acetals, 6-acetoxycyclohexa-2,4-di­enones, and their congeners, has stimulated widespread interest among organic chemists, and the use of such reactive species has emerged as a powerful method for the efficient synthesis of complex molecules. Our approach to create molecular complexity and diversity involves the oxidative dearomatization of 2-(hydroxymethyl)phenols to give spiro[cyclohexa-2,4-dienone-6,2′-oxiranes], followed by cycloaddition and transformation of the resulting adducts in the ground and excited states. In this account, we describe the evolution of the methodology and its application which has led to the development of novel and efficient routes to a diverse array of complex molecular architectures from simple aromatics. 1 Introduction 2 Cycloaddition of Cyclohexa-2,4-dienones of Types 3 and 4 and Manipulation of the Adducts in the Ground and Excited States 2.1 Cycloaddition of Cyclohexa-2,4-dienones of Types 3 and 4 : An Efficient Route to Functionalized and Appended Bicyclo[2.2.2]octanes 2.1.1 Cycloaddition of Cyclohexa-2,4-dienones of Types 3 and 4 with Electron-Deficient π-Partners 2.1.2 Cycloaddition of Cyclohexadienones of Type 4 with Vinyl Ethers and Vinyl Acetate 2.1.3 Cycloaddition of Cyclohexadienones of Types 3 and 4 with Acyclic 1,3-Dienes: Direct Entry to Bicyclo[2.2.2]octenones Having an endo -Vinyl Group 2.2 Manipulation of the Oxirane Moiety or the Chloromethyl and Hydroxy Groups in the Adducts: Synthesis of Embellished Bicyclo[2.2.2]octanes 2.3 3,3-Sigmatropic Shift in Bicyclo[2.2.2]octanes: A General Stereoselective Route to Functionalized cis -Decalin Derivatives 2.4 Sigmatropic Rearrangements of β,γ-Enones in Excited States: Stereoselective Routes to Bicyclo[3.3.0]- and Bi­cyclo[4.2.0]octanes and Tricyclic Compounds 3 Synthetic Applications 3.1 Synthesis of Hirsutic Acid C and the Framework of ­Pupukeananes from a Common Precursor 3.2 Chemistry of Fused Spiro[cyclohexa-2,4-dienone-6,2′-oxiranes] and Their Adducts: Synthesis of Propellanes and ­Steroid–Polyquinane Hybrids 3.2.1 A General Route to [3.3.3]- and [4.3.3]Propellanes 3.2.2 Synthesis of Steroid–Polyquinane Hybrids 3.3 Synthesis of Tri- and Tetracyclic Networks of Atisane Diterpenoids 3.3.1 Synthesis of Tricyclo[6.2.2.0 1,6 ]dodecanes and Their Homologues 3.3.2 Synthesis of the Tetracyclic Network of Atisane Diterpenoids: An Interesting Manifestation of Subtle Control by a Remote Functional Group 3.4 Intramolecular Cycloaddition of Cyclohexa-2,4-dienones: Synthesis of Platencin 4 Summary and Outlook

Synthesis of a tetracyclic ring system (BCDE) of atropurpuran is described. Oxidative dearomatization, cycloaddition of spiroepoxycyclohexa-2,4-dienone, radical cyclization, and a tandem oxidation–aldol–oxidation are the key features of our methodology.

A regio- and stereoselective cycloaddition of 6-chloromethyl-6-hydroxycyclohexa-2,4-dienones with benzofuran leading to dihydrobenzofuran annulated bicyclo[2.2.2]octenones having a beta,gamma-enone chromophore has been reported. Further transformation of adducts into benzannulated oxa-polyquinanes and dihydrobenzoftiran annulated bicyclo[4.2.0]octenones has also been described. (C) 2015 Elsevier Ltd. All rights reserved.

An efficient synthesis of annulated bicyclo[2.2.2]octane having beta,gamma-enone chromophoric system and triplet sensitized 1,2-acyl shift rearrangement leading to the formation of angular oxa-triquinane is described. Oxidative dearomatization, intramolecular Diels-Alder reaction of 6,6-spiroepoxycyclohexa-2,4-dienone and oxa-di-pi-methane reaction are the key features of our approach. (C) 2015 Elsevier Ltd. All rights reserved.

Synthesis of novel bicyclo[2.2.2]octenones endowed with a beta,gamma-enone system in which gamma-carbon is substituted with an electron-withdrawing group from simple aromatics is described. Oxa-di-pi-methane reaction of bicyclo[2.2.2]octenones to functionalized bicyclo[3.3.0]octanes and their transformation to bicyclo[3.2.1]octane framework are also presented.

Regio- and stereoselective cycloaddition of beta-nitroacrylates with electron deficient cyclohexa-2,4-dienones leading to highly functionalised bicyclo[2.2.2]octanes having the beta-nitroester group and their transformation to bicyclo[2.2.2]octanes having beta-aminoester functionality is described. (C) 2014 Elsevier Ltd. All rights reserved.