A Pauson−Khand and Ring-Expansion Approach to the Aquariane Ring System

The carbocyclic ring system of the aquariolide diterpenes has been synthesized by two routes involving a diastereoselective Pauson−Khand reaction and subsequent ring expansion. In one route, a tetracyclic enone was elaborated to generate the nine-membered ring by Grob fragmentation. In the second approach, a spirocyclic tricycle underwent a facile anionic oxy-Cope rearrangement to complete the synthesis of the desired ring system

Synthetic Studies toward the Kempane Diterpenes: Preparation of the Ring System

Synthetic Studies toward the Kempane Diterpenes:  Preparation of the Ring Syste

Reactions of 1,2-Bis(trimethylsilyloxy)cycloalkenes with the Diethyl Acetals of Aldehydes

Lewis acid-mediated reactions of 1,2-bis(trimethylsilyloxy)cyclobutene with acetals derived from a variety of aldehydes, followed by treatment with Amberlyst 15 resin in TFA, yielded 1,3-cyclopentanedione products, but reactions with 3,3-dimethyl-1,2-bis(trimethylsilyloxy)cyclobutene led to 1,2-cyclopentanediones. Reactions of 1,2-bis(trimethylsilyloxy)cyclopentene gave intermediates that did not undergo skeletal rearrangement with Amberlyst 15 resin in TFA

Synthesis of 5-Hydroxycyclopent-2-enones from Allenyl Vinyl Ketones via an Interrupted Nazarov Cyclization

Treatment of an allenyl vinyl ketone with trifluoroacetic acid leads to Nazarov cyclization, and the intermediate carbocation is trapped efficiently by trifluoroacetate. Hydrolysis of the ester with methanol and basic alumina provides, in good to excellent overall yield, a 5-hydroxycyclopent-2-enone in which the alcohol is predominantly trans to a substituent at C-4

Synthesis of the Tetracyclic Core of the Kempanes by a Ring-Closing Metathesis Strategy

The synthesis of the tetracyclic ring system of the kempane diterpenes was achieved through the highly regio- and stereoselective Diels−Alder reaction of an isopropenyl-diene with 2,6-dimethyl-p-benzoquinone, addition of an allyl group, and ring-closing metathesis of the isopropenyl and allyl groups

A Pauson−Khand and Ring-Expansion Approach to the Aquariane Ring System

The carbocyclic ring system of the aquariolide diterpenes has been synthesized by two routes involving a diastereoselective Pauson−Khand reaction and subsequent ring expansion. In one route, a tetracyclic enone was elaborated to generate the nine-membered ring by Grob fragmentation. In the second approach, a spirocyclic tricycle underwent a facile anionic oxy-Cope rearrangement to complete the synthesis of the desired ring system

A Pauson−Khand and Ring-Expansion Approach to the Aquariane Ring System

The carbocyclic ring system of the aquariolide diterpenes has been synthesized by two routes involving a diastereoselective Pauson−Khand reaction and subsequent ring expansion. In one route, a tetracyclic enone was elaborated to generate the nine-membered ring by Grob fragmentation. In the second approach, a spirocyclic tricycle underwent a facile anionic oxy-Cope rearrangement to complete the synthesis of the desired ring system

The BF₃·Et₂O-Catalyzed Reaction of 1,2-Bis[(trimethylsilyl)oxy]cyclobutene and Analogues with Aromatic Ketones

The BF3·Et2O-Catalyzed Reaction of 1,2-Bis[(trimethylsilyl)oxy]cyclobutene and Analogues with Aromatic Ketone

A Pauson−Khand and Ring-Expansion Approach to the Aquariane Ring System

The carbocyclic ring system of the aquariolide diterpenes has been synthesized by two routes involving a diastereoselective Pauson−Khand reaction and subsequent ring expansion. In one route, a tetracyclic enone was elaborated to generate the nine-membered ring by Grob fragmentation. In the second approach, a spirocyclic tricycle underwent a facile anionic oxy-Cope rearrangement to complete the synthesis of the desired ring system

Synthesis of 5-Hydroxycyclopent-2-enones from Allenyl Vinyl Ketones via an Interrupted Nazarov Cyclization

Treatment of an allenyl vinyl ketone with trifluoroacetic acid leads to Nazarov cyclization, and the intermediate carbocation is trapped efficiently by trifluoroacetate. Hydrolysis of the ester with methanol and basic alumina provides, in good to excellent overall yield, a 5-hydroxycyclopent-2-enone in which the alcohol is predominantly trans to a substituent at C-4