Unexpectedly Regioselective Diels-Alder Reactions of New Unsymmetrical Benzoquinones: A Convenient Synthetic Entry to Uniquely Substituted Decalins

We report flexible synthesis of new unsymmetrically 2,6-disubstituted benzoquinones (33 examples) and a systematic study of their reactivity in the Diels-Alder reaction. The Diels-Alder reactions of selected unsymmetrical benzoquinones with seemingly similar substituents were found to proceed with high regioselectivity and the formation of selected experimentally observed main products was rationalized by theoretical (DFT) calculations. The findings can be exploited in the convenient preparation of densely substituted and stereochemically defined decalins with unique angular substituents at ring fusion. We also demonstrate the usefulness of this methodology in complex molecule synthesis through the total synthesis of a novel forskolin analog possessing an ethyl group at the fusion of the rings B and C.

From perfluoroalkyl aryl sulfoxides to ortho thioethers

Access to original ortho thioether derivatives was achieved through a [3,3]-rearrangement in a one-pot two-step protocol. Several aryl-SCF3 compounds are reported by variation of the nitrile or of the trifluoroalkyl sulfoxide starting material. The variation of the perfluoroalkyl chain was also possible.

Synthesis of benzo[b]furans from alkynyl sulfoxides and phenols by the interrupted Pummerer reaction

The interrupted Pummerer reaction of alkynyl sulfoxides with phenols is disclosed. A wide range of benzo[b]furans were efficiently synthesized through unexplored electrophilic activation of the electron-deficient alkynyl sulfinyl group. Based on the good availability of alkynyl sulfoxides, we successfully prepared various functionalized benzo[b]furans from readily available alkynes, thiosulfonates, and phenols.

Dearomative di- and trifunctionalization of aryl sulfoxides via [5,5]-rearrangement

Aromatic [5,5]-rearrangement can in principle be an ideal protocol to access dearomative compounds. However, the lack of competent [5,5]-rearrangement impedes the advance of the protocol. In this Article, we showcase the power of [5,5]-rearrangement recently developed in our laboratory for constructing an intriguing dearomative sulfonium specie which features versatile and unique reactivities to perform nucleophilic 1,2- and 1,4-addition and cyclization, thus achieving dearomative di- and trifunctionalization of easily accessible aryl sulfoxides. Impressively, the dearomatization products can be readily converted to sulfur-removed cyclohexenones, naphthalenones, bicyclic cyclohexadienones, and multi-substituted benzenes. Mechanistic studies shed light on the key intermediates and the remarkable chemo-, regio- and stereoselectivities of the reactions.

Sulfoxide synthesis from sulfinate esters under Pummerer-like conditions

A facile synthetic method for the preparation of allyl sulfoxides by S-allylation of sulfinate esters proceeds through sulfonium intermediates without [3,3]-sigmatropic rearrangement and further Pummerer-type reactions of the resulting allyl sulfoxides. On the basis of the plausible reaction mechanism involving sulfonium salt intermediates, S-alkynylation and S-arylation were also accomplished.

Sulfoxide-mediated oxidative cross-coupling of phenols

A metal-free, oxidative coupling of phenols with various nucleophiles, including arenes, 1,3-diketones and other phenols, is reported. Cross-coupling is mediated by a sulfoxide which inverts the reactivity of the phenol partner. Crucially, the process shows high selectivity for cross-versus homo-coupling and allows efficient access to a variety of aromatic scaffolds including biaryls, benzofurans and, through an iterative procedure, aromatic oligomers.

A metal-free, oxidative coupling of phenols with various nucleophiles, including arenes, 1,3-diketones and other phenols, is reported.