Convenient Access to Bicyclic and Tricyclic Diazenes

Heating the tosylhydrazone of an ω-alkenyl ketone or aldehyde to reflux in toluene in the presence of K2CO3 delivered the bicyclic diazene. Irradiation of the diazene converted it to the cyclopropane. This appears to be a generally useful method for the construction of substituted cyclopentanes and cyclohexanes

A Synthetic Approach to 15-D_2c-Isoprostane Ethyl Ester

The preparation of ketone 10 is described. Oxidation of 10 to the sulfoxide followed by sigmatropic rearrangement gave not the expected 15-D2c-isoprostane ethyl ester (4), but the trans diastereomer 11. A 13C NMR method for establishment of the relative configuration of the cyclopentane rings of the isoprostanes and prostaglandins is also reported

Alkylation of Acetonitrile

Alkylation of Acetonitril

Total Synthesis of the Four Enantiomerically Pure Diastereomers of 8-F_2t-Isoprostane

Syntheses of the four enantiomerically pure diastereomers of 8-F2t-isoprostane (5−8) are described. The key to this approach was to prepare the racemic alcohol 9 in high diastereomeric purity and then resolve 9 by lipase-mediated acetylation to yield the enantiomerically pure alcohols 30 and 32

Synthesis of α-Necrodol: Unexpected Formation of a Cyclopropene

Significant 1,3-induction in intramolecular alkylidene C−H insertion is reported. Thus, exposure of ketone I to the lithium salt of (trimethylsilyl)diazomethane provides a 2.4:1.0 ratio of IIa and IIIa, which are deprotected to α-necrodol IIb and the epimeric IIIb. The 1,3-insertion product cyclopropene IV was also formed

Diastereoselective Rh-Mediated Construction of 2,3,5-Trisubstituted Tetrahydrofurans

Dirhodium(II) carboxylate catalyzed cyclization of a series of γ-alkoxy-α-diazo esters 1 has been shown to proceed with substantial diastereoselectivity, producing the 2,3,5-trisubstituted tetrahydrofurans 2 and 3. The diastereoselectivity of the cyclization improved as the electron-withdrawing ability of the substituent R increased. A mechanistic hypothesis is presented

Convenient Access to Bicyclic and Tricyclic Diazenes

Heating the tosylhydrazone of an ω-alkenyl ketone or aldehyde to reflux in toluene in the presence of K2CO3 delivered the bicyclic diazene. Irradiation of the diazene converted it to the cyclopropane. This appears to be a generally useful method for the construction of substituted cyclopentanes and cyclohexanes

Construction of the Tricyclic A‑B‑C Core of the <i>Veratrum</i> Alkaloids

Organocatalyzed enantioselective allylation of 2-iodocyclohexenone followed by methylation and oxy-Cope rearrangement delivered enantiomerically enriched 2-methyl 3-allyl cyclohexanone, which engaged in acid-catalyzed Robinson annulation to give the bicyclic enone. Subsequent elaboration of the pendant allyl group into an α-diazo β-keto ester set the stage for Rh-mediated cyclization to deliver the tricyclic A-B-C core of the Veratrum alkaloids

Total Synthesis of the Ethyl Ester of the Major Urinary Metabolite of Prostaglandin E₂

The preparation of the ethyl ester of the major urinary metabolite of prostaglandin E2 3 is described. The key step is the kinetic opening of the TBS-protected bicyclic ketone 7 with thiophenol

Diastereoselective Rh-Mediated Construction of 2,3,5-Trisubstituted Tetrahydrofurans

Dirhodium(II) carboxylate catalyzed cyclization of a series of γ-alkoxy-α-diazo esters 1 has been shown to proceed with substantial diastereoselectivity, producing the 2,3,5-trisubstituted tetrahydrofurans 2 and 3. The diastereoselectivity of the cyclization improved as the electron-withdrawing ability of the substituent R increased. A mechanistic hypothesis is presented