Michiharu Kato

Solid State Acetylation with Acetylimidazole: Selective Protection of Primary Alcohols and Phenols

Abstract Primary alcohols and phenols have been acetylated with acetylimidazole by the solid state reaction, grinding both substrates with a pestle in a mortar.

Carbocyclic construction by the [2,3]sigmatropic rearrangement of cyclic sulfonium ylides. a new entry for the stereoselective synthesis of substituted cyclohexanones

Abstract The rhodium(II)-catalyzed cyclization of acyclic α-diazo-β-keto esters 1c,d provided stereoselectively the highly substituted cyclohexanones 3c,d respectively, by the [2,3]sigmatropic rearrangement via stereocontrolled nine-membered allylsulfonium ylides 2c,d. Further elaboration of 3d toward the cyclohexanone 36 accomplished asymmetric formal syntheses of the representative elemanoids, 37 and 38. The compound 3c was transformed into the cyclohexanone 34a and cyclohexene 43, which could serve as the key intermediates for the synthesis of natural products possessing contigously cis-arranged trimethylcyclohexanone and its related moieties, respectively.

Facile preparation of thiocarbonylimidazolide by organic solid state reaction

Abstract Thiocarbonylimidazolide 3 has been prepared from alcohol 1 and thiocarbonyldiimidazole 2 by grinding both substrates with pestle and mortar.

The reaction of 2-arylsulfonyloxytropones and active methylene compounds: The formation of 8-hydroxy-2H-cyclohepta[b]furan-2-one and 2-amino-8H-cyclohepta[b]furan-8-one derivatives

Abstract Reaction of 2-arylsulfonyloxytropones (IV) and active methylene compounds, diethyl malonate, ethyl acetoacetate, ethyl cyanoacetate, malononitrile or cyanoacetamide, in the presence of NaOEt give 8-hydroxy-2H-cyclohepta[b]furan-2-one derivatives (V) and/or 2-amino-8H-cyclohepta[b]furan-8-one derivatives (VII), in addition to azulene derivatives (1) or 2H-cyclohepta(b]furan-2-one derivatives (II), known to be obtained by the reaction of 2-chlorotropones or 2-methoxytropones with active methylene compounds. Relative yields of products are influenced markedly by conditions, e.g. base type or molar ratios. The formation of V and VII is characteristic of 2-arylsulfonyloxytropones, not being observed with 2-chlorotropones or 2-methoxytropones. A reaction course involving elimination of the arylsulfonyl group as arenesulfinate ion is presented.

Organic Reaction Without Solvent. Efficient Synthesis of Thiocarbonylimidazolide

Abstract Thiocarbonylimidazolide has been prepared from thiocarbonyl-diimidazole and alcohol simply by grinding in a mortar at ambient temperature.

Total synthesis of dl-siccanin and dl-siccanochromene E

Abstract The stereoselective synthesis of dl -siccanin (1) and dl -siccano-chromene E (2) has been described. Acid isomerization of nonconjugated octalone 11a, derived from known octalone 5, stereoselectively provided cis-fused octalone 12, from which cis -drimane aldehyde 31 was obtained. After condensation of 31 with lithio-orcinol dimethyl ether, the product 32 was treated with pyridinium chloride to give tetrahydrofuran 33 whose complete stereostructure was unambiguously established by an X-ray crystal analysis. While cyclization of monophenol 34, obtained by partial demethylation of 33, with sulfuric acid afforded siccanochromene E methyl ether (35), reaction of 34 with Lewis acid gave siccanin methyl ether (36) along with 35. In the latter cyclization, the formation of 36 was demonstrated to occur from initially formed 35. Finally, demethylation of 35 and 36 provided 2 and 1, respectively. A novel tetrahydrofuran formation by a neighboring participation, which was observed in hydroxy ketone 24 and diol 32, are also discussed.

Efficient preparation of (R)-(–)-cryptone from (+)-nopinone and its transformation into noroxopenlanfuran

Starting with (R)-(–)-cryptone, prepared in 42% overall yield from (+)-nopinone in five steps, the first synthesis of noroxopenlanfuran was accomplished, confirming its absolute configuration.

Novel synthesis of degradation products of carotenoids,megastigmatrienone analogues and blumenol-A

Synthesis of 4-alkylidene-3,5,5-trimethylcyclohex-2-enones 7 has been achieved utilising 1,4-conjugate dehydrobromination of allylic bromides 5 as a key step. This chemical transformation is applied to the synthesis of degradation products of carotenoids: megastigmatrienones 7e/1–4, 4-methylene-3,5,5-trimethylcyclohex-2-enone 7a, 4-(3-hydroxybutylidene)-3,5,5-trimethylcyclohex-2-enone 9, 1,3,7,7-tetramethyl-2-oxabicyclo[4.4.0]dec-5-en-9-one 10a–b and 3,4,7,8-tetrahydro-4,4,7-trimethylnaphthalen-2(6H)-one 15. A novel photoisomerisation of 4-[(Z )-3-acetoxybut-2-enyl]-4-hydroxy-3,5,5-trimethylcyclohex-2-enone 19 to 4-[(E )-3-acetoxybut-2-enyl]-4-hydroxy-3,5,5-trimethylcyclohex-2-enone 20 enables us to synthesise blumenol-A 21.

An efficient and convenient synthesis of bridged δ-lactones

endo-4-Ethoxycarbonyl-4-(phenylthio)-9-methylene-2-oxabicyclo-[3.3.1]nonan-3-ones (5a–c) and their related compounds 5e–h, endo-4-ethoxycarbonyl-4-(phenylthio)-8-methylene-2-oxabicyclo[3.2.1]octan-3-one (5d) were synthesized from α-diazomalonates 3 of 2-(phenylthio)cyclohex-2-en-1-ols (1a–c) and their related compounds e–h, and 2-(phenylthio)cyclopent-2-en-1-ol (1d), respectively, via the [2,3]sigmatropic rearrangement of cyclic allylsulfonium ylides 4.

Total synthesis of (±)-seychellene

The total synthesis of (±)-seychellene (4,7,8-trimethyl-11-methylenetricyclo[5.3.1.03,8]undecane)(I) from2,3-di-methylcyclohex-2-en-1-one (XIV) is described. The ketone (XIV) was converted into 2-methyl-2-(3-methyl-5-iodopentyl)-3-methylenecyclohexan-1-one (XV), which gave 2-methyl-2-(3-methyl-5-iodopentyl)-3-bromo-methylcyclohexa-3,5-dien-1-one (XIX) with N-bromosuccinimide. Treatment of bromo-ketone (XIX) with chromium(II) chloride followed by acid gave 2,3-dimethyl-2-(3-methyl-5-iodopentyl)cyclohexa-3,5-dien-1-one (XXI). 2,3-Dimethyl-2-(3-methyl-5-dimethylaminopentyl)cyclohexa-3,5-dien-1-one (XXII) was obtained from the dienone (XXI) and was oxidised; pyrolysis of the resulting N-oxide yielded 4,7,8-trimethyltricyclo-[5.3.1.03,8]undec-9-en-11-one (VII). The adduct (VII) was hydrogenated to (±)-norseychellanone (4,7,8-trimethyltricyclo[5.3.1.03,8]undecan-11 -one), whose transformation into (±)-seychellene is known.