One-pot dehydrogenation of carboxylic acid derivatives to α,β-unsaturated carbonyl compounds under mild conditions

Alcohol Dehydrogenase‐Catalyzed Synthesis of Enantiomerically Pure δ‐Lactones as Versatile Intermediates for Natural Product Synthesis

“…[17d,23] Although the reaction was carried out successfully, the obtained product could not be completely separated from undesired byproducts by means of flash chromatography or MPLC, so that goniothalamine (4a) was isolated in 49% yield containing some impurities. Finally, we took advantage of a protocol by Matsuo and Aizawa, [24] using N-tert-butylbenzenesulfinimidoyl chloride (12) as reagent for the one-pot dehydrogenation of carboxylic acid derivatives to a,b-unsaturated carbonyl compounds. By this method, intermediates 6a-c could readily be converted into the target compounds 4a-c after generation of the corresponding lithium enolates by treatment with LDA in THF at À78 8C giving highly reproducible yields of 57-63%; all by-products were removable by flash chromatography (Scheme 8).…”

Preparation of N-(α,β-unsaturated acyl)-sulfonamides

“…1 H NMR (300 MHz) and 13 C NMR (75 MHz) spectra were recorded in CDCl 3 (with TMS for 1 H and chloroform-d for 13 C as the internal standard). Elemental analyses were carried out by the Analytical Laboratory in the Center for Heterocyclic Compounds, Department of Chemistry, University of Florida.…”

Collective Total Synthesis of Aspidofractinine Alkaloids through the Development of a Bischler–Napieralski/Semipinacol Rearrangement Reaction

“…Direct amide reduction of 23 with in situ prepared AlH 3 would produce N ‐methyl‐aspidofractinine ( 2 ) in 87 % yield, [15] which upon selective oxidation of the N ‐methyl group with benzyltriethylammonium permanganate would generate N ‐formyl‐aspidofractinine ( 3 ) in 75 % yield [3a] . Similarly, desaturation of 23 followed by amide reduction of the same AlH 3 conditions would provide N ‐methyl‐14,15‐didehydroaspidofractinine ( 4 ) in 42 % yield [15, 16] . The spectra data of our synthetic 2 and 4 are consistent with those in previous reports.…”