Highly Efficient Synthesis of Terminal Alkenes from Ketones

Abstract

[reaction: see text] The rhodium(I)-catalyzed methylenation of ketones using trimethylsilyldiazomethane proceeds to give the corresponding alkenes in good yields (60-97%). The use of an excess of 2-propanol and 1,4-dioxane as a solvent were instrumental to obtain the desired alkenes in high yields. Superior results were achieved with the rhodium(I)-catalyzed methylenation in comparison with the standard Wittig reaction.

Synthesis of 2-(2-phenylethenyl) substituted 4,5-dihydrofurans by regioselective addition of 1,3-dicarbonyl compounds to dienes promoted by cerium(IV) ammonium nitrate

“…Conjugated dienes 1-phenyl-1,3-butadiene 2a 43 and 3-methyl-1-phenyl-1,3-butadiene 2b 44 were synthesized from the reaction of methyl-triphenylphosphonium bromide and suitable carbonyl compounds in the presence of NaH/THF. 1,1-Diphenyl-1,3-butadiene 2c 45 was prepared from water elimination of alcohol obtained from Grignard reaction of benzophenone and allylmagnesium bromide.…”

“…2-phenylvinyl]-3,5,6,7-tetrahydro-1-benzofuran-4(2H)-one (3a) 2-Phenylvinyl]-3,5,6,7-tetrahydro-1-benzofuran-4(2H)-one (3b) 2-phenylvinyl]-3,5,6,7-tetrahydro-1-benzofuran-4(2H)-one (3c) 2-phenylvinyl]-3,5,6,7-tetrahydro-1-benzofuran-4(2H)-one (3j). 44,45 Colourless oil, yield 92%, 259 mg, …”

PSiP-Pincer Type Palladium-Catalyzed Dehydrogenative Borylation of Alkenes and 1,3-Dienes

“…All operations except workup and purification were performed under an argon atmosphere. 1 H and 13 C NMR spectra were recorded on a Bruker DRX-500 (500 MHz for 35 were known compounds in literature and others were commercially available. The geometry of the obtained boronic esters was determined by coupling constants between two olefinic protons or by NOE measurement.…”

Total Syntheses of Lyconadins: Finding Efficiency and Diversity

“…In this aza-[4+2] cyclization, C 6 -N and C 9 -C 10 bonds, whose construction had required multiple steps in the previous synthesis, were formed in one step and formaldehyde served well as a one-carbon stitching unit. Compound 30 was quickly advanced to known enone 22 with a sequence of Lebel olefination 21 and allylic oxidations. Using the Fukuyama 2-pyridone synthesis protocol, we were able to complete a short total synthesis of lyconadin A.…”