Photoinduced Decarbonylative Rearrangement of Bicyclo[2.2.2]Octenones: Synthesis of the Marasmane Skeleton

The marasmane sesquiterpenoid structure can be found in the skeleton of a variety of natural products bearing interesting bioactivity. The unique fused-5,6,3-tricyclic ring structure, in which the rings are <i>cis</i>-fused and the five- and three-membered rings are mutually <i>trans</i>, provides a synthetic challenge for organic chemists. In this work, we took advantage of the photoinduced decarbonylative rearrangement of bicyclo[2.2.2]­octenone to develop a new methodology for construction of the highly functionalized fused-5,6,3-tricyclic ring structure in a concise reaction sequence

A Dinuclear Palladium Catalyst for α-Hydroxylation of Carbonyls with O₂

A chemo- and regioselective α-hydroxylation reaction of carbonyl compounds with molecular oxygen as oxidant is reported. The hydroxylation reaction is catalyzed by a dinuclear Pd(II) complex, which functions as an oxygen transfer catalyst, reminiscent of an oxygenase. The development of this oxidation reaction was inspired by discovery and mechanism evaluation of previously unknown Pd(III)−Pd(III) complexes

Photoinduced Decarbonylative Rearrangement of Bicyclo[2.2.2]Octenones: Synthesis of the Marasmane Skeleton

The marasmane sesquiterpenoid structure can be found in the skeleton of a variety of natural products bearing interesting bioactivity. The unique fused-5,6,3-tricyclic ring structure, in which the rings are <i>cis</i>-fused and the five- and three-membered rings are mutually <i>trans</i>, provides a synthetic challenge for organic chemists. In this work, we took advantage of the photoinduced decarbonylative rearrangement of bicyclo[2.2.2]­octenone to develop a new methodology for construction of the highly functionalized fused-5,6,3-tricyclic ring structure in a concise reaction sequence

Photoinduced Decarbonylative Rearrangement of Bicyclo[2.2.2]Octenones: Synthesis of the Marasmane Skeleton

The marasmane sesquiterpenoid structure can be found in the skeleton of a variety of natural products bearing interesting bioactivity. The unique fused-5,6,3-tricyclic ring structure, in which the rings are <i>cis</i>-fused and the five- and three-membered rings are mutually <i>trans</i>, provides a synthetic challenge for organic chemists. In this work, we took advantage of the photoinduced decarbonylative rearrangement of bicyclo[2.2.2]­octenone to develop a new methodology for construction of the highly functionalized fused-5,6,3-tricyclic ring structure in a concise reaction sequence

A Dinuclear Palladium Catalyst for α-Hydroxylation of Carbonyls with O₂

A chemo- and regioselective α-hydroxylation reaction of carbonyl compounds with molecular oxygen as oxidant is reported. The hydroxylation reaction is catalyzed by a dinuclear Pd(II) complex, which functions as an oxygen transfer catalyst, reminiscent of an oxygenase. The development of this oxidation reaction was inspired by discovery and mechanism evaluation of previously unknown Pd(III)−Pd(III) complexes

Efficient Synthesis and Subsequent Transformations of Phenylsulfanylbicyclo[2.2.2]octenones and Phenylselenylbicyclo[2.2.2]octenones

Inverse-electron-demand Diels−Alder reactions of masked o-benzoquinones 2 with phenyl vinyl sulfide and phenyl vinyl selenide furnished highly functionalized bicyclo[2.2.2]octenone derivatives 3 and 4, respectively, in excellent regio- and stereoselectivities and yields up to 90%. The bicyclo[2.2.2]octenone derivatives 3 with the sulfur functionality were subjected to an oxidation−elimination process to furnish bicyclo[2.2.2]octadienone systems 7 in good yields. During the reduction process, the Diels−Alder adducts 3e and 4e led to 8, whereas the carbon-centered radicals generated from the other adducts 3a−d and 4a−d provided various rearranged products 9−13 depending on the substitution pattern and reagents utilized (Raney-Ni or n-Bu3SnH). Surprisingly these radicals showed preference for the carbonyl functionality to the olefinic double bond, leading to interesting rearrangement reactions of mechanistic importance and possible synthetic utility. Interestingly the alcohols obtained from the reduction of Diels−Alder adducts 3a−d underwent desulfurization smoothly to give desulfurized products in high yields; thus a detoured method of “reduction−desulfurization−oxidation” provides an entry to desulfurized bicyclo[2.2.2]octenones without rearrangement

Photoinduced Decarbonylative Rearrangement of Diazabicyclo[2.2.2]Octenones: A Photochemical Approach of Diazabicyclo[4.1.0]heptene Skeleton from Masked <i>o</i>‑Benzoquinone

We report a photoinduced decarbonylative rearrangement of diazabicyclo[2.2.2]­octenone in the facile synthesis of a functionalized diazabicyclo[4.1.0]­heptene skeleton, a unique derivative of the hydropyridazine type structure which could be found in a variety of biologically active natural products. The scope of functional group compatibility in the photoreaction was examined by taking advantage of the easy access of the heterobicyclo[2.2.2] structure from the Diels–Alder reaction of masked o-benzoquinones. 4-Phenyl-1,2,4-triazoline-3,5-dione served as the dienophile which provided the adjacent N–N unit in hexahydropyridazine-type products of subsequent photorearrangement

Efficient Synthesis and Subsequent Transformations of Phenylsulfanylbicyclo[2.2.2]octenones and Phenylselenylbicyclo[2.2.2]octenones

Inverse-electron-demand Diels−Alder reactions of masked o-benzoquinones 2 with phenyl vinyl sulfide and phenyl vinyl selenide furnished highly functionalized bicyclo[2.2.2]octenone derivatives 3 and 4, respectively, in excellent regio- and stereoselectivities and yields up to 90%. The bicyclo[2.2.2]octenone derivatives 3 with the sulfur functionality were subjected to an oxidation−elimination process to furnish bicyclo[2.2.2]octadienone systems 7 in good yields. During the reduction process, the Diels−Alder adducts 3e and 4e led to 8, whereas the carbon-centered radicals generated from the other adducts 3a−d and 4a−d provided various rearranged products 9−13 depending on the substitution pattern and reagents utilized (Raney-Ni or n-Bu3SnH). Surprisingly these radicals showed preference for the carbonyl functionality to the olefinic double bond, leading to interesting rearrangement reactions of mechanistic importance and possible synthetic utility. Interestingly the alcohols obtained from the reduction of Diels−Alder adducts 3a−d underwent desulfurization smoothly to give desulfurized products in high yields; thus a detoured method of “reduction−desulfurization−oxidation” provides an entry to desulfurized bicyclo[2.2.2]octenones without rearrangement

Formal Synthesis of (±)-Pentalenolactone A Methyl Ester

We report the formal synthesis of (±)-pentalenolactone A methyl ester from simple 2-methoxyphenol. The key features of our route are as follows: a Diels–Alder reaction of masked o-benzoquinone to assemble the functionalized bicyclo[2.2.2]­octenone, a continuous-flow oxa-di-π-methane rearrangement for building the diquinane core (AB ring), and an oxidative cleavage/oxidation sequence for annulation of the δ-lactone (C ring)

Formal Synthesis of (±)-Pentalenolactone A Methyl Ester

We report the formal synthesis of (±)-pentalenolactone A methyl ester from simple 2-methoxyphenol. The key features of our route are as follows: a Diels–Alder reaction of masked o-benzoquinone to assemble the functionalized bicyclo[2.2.2]­octenone, a continuous-flow oxa-di-π-methane rearrangement for building the diquinane core (AB ring), and an oxidative cleavage/oxidation sequence for annulation of the δ-lactone (C ring)