An Improved Synthesis of 4-Cycloheptenone

A previous paper² described the chemistry of 1-aza-4-cyclo-octene 1 which we prepared from 4-cycloheptenone 2 according to the method of Bahurel et al.³ This procedure involves the condensation of cis-1,4-dichloro-2-butene with ethyl sodio-acetoacetate, yielding, a mixture of four isomers 3–6. The entire mixture is then heated with aqueous potassium hydroxide under reflux for four hours. Under these conditions 5 undergoes decarbethoxylation to yield 4-acetylcyclopentene 7, while 3 yields 2, presumatly by Cope rearrangement atid decarbethoxylation (2 is present in almost negligiblequantity but was reported³ to also yield 2).     

A Conventient Synthesis of 3-Hydroxy-4-chromanone Using Iodobenzene Diacetate

A useful synthesis of 3-hydroxy-4-chromanone (6) is not currently available. Lead tetraacetate oxidation of 4-chromanone (4) yields the C(3) acetoxy derivative but this compound could not be deacetylated to 6.¹ Recently Donnelly and Maloney reported² that the Algar-Flynn-Oyamada reaction (H₂O₂/CH₃OH/NaOH), which is commonly used for the conversion of o-hydroxychalcones (1) into 3-hydroxyflavanone (2) and 3-hydroxyflavones (3), does not yield 6 when applied to o-hydroxya-crylophenone 1 (R = H). The authors found that under less basic conditions using K₂CO₃ some 6 is formed but the major product is catechol. These observations clearly indicate the necessity of developing a method for making 6. The present note describes a staightforward way of preparing 3-hydroxy-4-chromanone (6) in good yield.     

Alumina-Assisted Basic Hydrolysis of Esters1

“Anhydrous hydroxide” formed by reaction of 2 equiv of potassium tert-butoxide with 1 equiv of water in dry ether serves as a useful reagent for hydrolyzing esters and tertiary amides at ambient temperatures.² During the course of our studies dealing with alumina as a support and as a catalyst for solid-liquid biphase reactions, we have discovered that potassium hydroxide crushed together with neutral alumina (reagent 1) provides the basis for an equally effective means for carrying out ester hydrolysis.^3,4 Moreover, isolation of the alcohol is readily accomplished by simple filtration and solvent evaporation.     

The Nitro Ketal Approach to Furane Systems. Total Synthesis of Racehic Bilobanone

Continuing our studies with the chemistry of ketals of β-nitro ketones¹, we wish to describe a new furane synthesis exemplified by a total synthesis of the sesquiterpene bilobanone 1 ².     

An Unusual Aminal Derivative from a Misdirected Gabriel Synthesis

N-(2-Bromoethyl)phthalimide (1) was reacted with sodium imidazolate in DMF to give the novel aminal N-[1-(1H-imidazol-1-yl)ethyl]phthalimide (4a) as well as N-vinylphthalimide (3) and the desired Gabriel intermediate 2. Aminal 4a as well as heterologues 4b - d form directly from reaction of 3 with the appropriate heterocyclic sodium salt.