Total synthesis of tetracyclic sesquiterpenoids: (±)-ishwarone

1980 ◽  
Vol 58 (23) ◽  
pp. 2613-2623 ◽  
Author(s):  
Edward Piers ◽  
Tse-Wai Hall
Keyword(s):  
Total Synthesis ◽  
Phase Transfer ◽  
Aqueous Sodium Hydroxide ◽  
Pyridinium Chlorochromate ◽  
Aqueous Sodium ◽  
Standard Methodology ◽  
Propargylic Alcohol ◽  
Crude Product ◽  
Hexamethyl Phosphoramide ◽  
Hydrolysis Of

A stereoselective total synthesis of the racemic modification of the tetracyclic sesquiterpenoid ishwarone (2) is described. Treatment of the known ketal aldehyde 19 with dibromomethylenetriphenylphosphorane gave the dibromo alkene 20, which was transformed efficiently into the propargylic alcohol 21. The latter compound was converted via the intermediates 22–24 into the octalone 12, which in turn was transformed by standard methodology into the corresponding ketal 7. Treatment of 7 with bromoform–aqueous sodium hydroxide in the presence of a phase-transfer catalyst, followed by acid hydrolysis of the resultant crude product, gave the crystalline keto dibromide 27. When a solution of the corresponding ketal 26 in tetrahydrofuran–hexamethyl-phosphoramide containing methyl iodide was treated with tert-butyllithium, the monobromo ketals 28 (58%) and 29 (38%) were formed. Compound 28 was converted by means of conventional reactions into the keto alcohol 32. Attempts to transform the latter substance into (±)-ishwarone (2) proved unsuccessful. When the olefinic ketal 7 was allowed to react with dimethyl diazomalonate in the presence of copper bronze, the diester 44 was produced in good yield. The latter intermediate was converted via standard methodology into the keto dimesylate 47 which, upon reaction with lithium chloride in ether–hexamethylphosphoramide, gave the corresponding dichloride 48. Treatment of 48 with potassium tert-butoxide in tetrahydrofuran resulted in an intramolecular alkylation to provide the tetracyclic keto chloride 50. Reduction of 50 with lithium triethylborohydride in tetrahydrofuran afforded (±)-ishwarol (51) which, upon oxidation with pyridinium chlorochromate in dichloromethane, furnished (±)-ishwarone (2).

Preparation and thermal rearrangement of trans-3-[1-methyl-2-(2-methyl-1-propenyl)cyclopropyl]-2-cyclohexen-1-one. A synthesis of (±)-[β-himachalene

1983 ◽  
Vol 61 (6) ◽  
pp. 1239-1247 ◽  
Author(s):  
Edward Piers ◽  
Edward H. Ruediger
Keyword(s):  
Total Synthesis ◽  
Wittig Reaction ◽  
Phase Transfer ◽  
Aqueous Sodium Hydroxide ◽  
Butyl Alcohol ◽  
High Yield ◽  
Thermal Rearrangement ◽  
Aqueous Sodium ◽  
Tert Butyl Alcohol ◽  
Enol Phosphate

A total synthesis of the sesquiterpenoid (±)-β-himachalene (2) is described. Treatment of 5,5-dimethyl-2-vinyl-1,3-dioxane (24) with bromoform and aqueous sodium hydroxide in the presence of a phase-transfer catalyst afforded the dibromocyclopropane 25. When the latter substance was allowed to react (tetrahydrofuran–hexamethylphosphoramide, −95 °C) with n-butyllithium in the presence of methyl iodide, a mixture of the epimeric products 26 (87–93%) and 27 (7–13%) was produced in high yield. Compound 26 was converted via a two-step sequence (hydrolysis with 88% formic acid, 26 → 28; Wittig reaction with isopropylidenetriphenylphosphorane, 28 → 16) into the bromocyclopropane 16, which was transformed into the cuprate reagent 17. Reaction of 3-iodo-2-cyclohexen-1-one (4) with reagent 17, followed by thermolysis (xylene, reflux) of the resultant product 18 (the title compound), afforded, in quantitative yield, the dienone 12. Methylation of 12 furnished compound 29 which, upon hydrogenation in the presence of tris(triphenylphosphine)chlororhodium, gave the ketone 32. Conversion of compound 32 into the corresponding enol phosphate 33, followed by reduction (lithium, ethylamine–tetrahydrofuran, tert-butyl alcohol) of the latter material, provided (±)-β-himachalene (2).

Five-membered ring spiro-annulation via thermal rearrangement of enol silyl ethers of 2-(cyclopropylmethylene)cycloalkanones. A formal total synthesis of some spirovetivane-type sesquiterpenoids

1983 ◽  
Vol 61 (2) ◽  
pp. 288-297 ◽  
Author(s):  
Edward Piers ◽  
Cheuk Kun Lau ◽  
Isao Nagakura
Keyword(s):  
Total Synthesis ◽  
Acid Hydrolysis ◽  
Pyridinium Chlorochromate ◽  
Thermal Rearrangement ◽  
Similar Sequence ◽  
Silyl Ethers ◽  
Tertiary Alcohols ◽  
Enolate Anion ◽  
Enol Silyl Ethers ◽  
Hydrolysis Of

Treatment of the 2-(iodomethylene)cycloalkanones 10 and 11 with lithium (phenylthio)(cyclopropyl)cuprate provided good yields of the corresponding β-cyclopropyl enones 12 and 13, respectively. Thermolysis of the latter substances produced relatively poor yields of the desired spiro-annulation products 14 and 15. However, conversion of 12 and 13 into the corresponding enol silyl ethers 24 and 25, followed by thermal rearrangement of the latter materials and acid hydrolysis of the resulting products, provided synthetically useful yields of the spiro enones 14 and 15. Cuprous iodide-catalyzed addition of methyl magnesium iodide to 2-cyclohexen-1-one, followed by trapping of the resultant enolate anion with cyclopropanecarboxaldehyde, provided the ketols 38, which could be converted readily into the mixture of enol silyl ethers 34 and 35. Thermal rearrangement of the latter substances gave, after acid hydrolysis of the crude thermolysate, the spiro enones 42 and 43 in a ratio of ~2.5:1 (57% yield). Treatment of 42 with methyllithium in ether gave the tertiary alcohols 44 and 45 (ratio ~4:1). Hydroboration (disiamylborane, tetrahydrofuran; H2O2, NaOH) of 44, followed by oxidation of the resultant diol 46 with pyridinium chlorochromate, provided the ketol 47. A similar sequence of reactions converted the olefinic alcohol 45 into the ketol 49. Dehydration (p-toluenesulfonic acid in benzene) of 47 gave the spiro enones 28 and 48, in a ratio of ~9:1. Compound 28, also prepared previously from the ketol 49, had been converted earlier into the spirovetivane-type sesquiterpenoids (±)-α-vetispirene (29), (±)-β-vetivone (30), (±)-hinesol (31), (±)-hinesol acetate (32), and (±)-agarospirol (33).

KINETICS OF THE ALKALINE HYDROLYSIS OF PROPIONITRILE

1942 ◽  
Vol 20b (9) ◽  
pp. 185-188 ◽  
Author(s):  
B. S. Rabinovitch ◽  
C. A. Winkler
Keyword(s):  
Activation Energy ◽  
Sodium Hydroxide ◽  
Alkaline Hydrolysis ◽  
Aqueous Sodium Hydroxide ◽  
Alkali Concentration ◽  
Aqueous Sodium ◽  
Velocity Constant ◽  
Total Ammonia ◽  
Kinetics Of ◽  
Hydrolysis Of

Some contradictory points recorded for the alkaline hydrolysis of nitriles have been clarified by a study of propionitrile hydrolysis in aqueous sodium hydroxide solutions of concentration 0.3 to 4 N. It has been shown that the rate of alkaline hydrolysis of propionitrile is given by the rate of formation of total ammonia and intermediate amide and not by that of ammonia alone. The relative rates of propionitrile and propionamide hydrolysis were found to be approximately 1:10 over the whole alkali concentration range. The bimolecular velocity constant is essentially independent of alkali concentration. An activation energy of 20,300 cal. was determined for the reaction in 0.65 N alkali.

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