No abstract

Direct irradiation of 2-methyl-2-(cyclopent-l-eny1)cyclopentanone (1) gives the hydroazulene (Z), whereas the tricyclic ketone (4) is produced upon sensitized irradiation in acetone.

a t 0 "C and was then poured over ice containing 2 N hydrochloric acid (4 equiv). T h e product was then extracted i n t o ether. T h e ether solution was dried and evaporated under vacuum, and the product was distilled.3,3,5,5-Tetramethylcyclohexanone (18). By the above procedure compound 18 was formed in 76% yield from 16 g (0.1 mol) o f chloride 7a and in 80% yield from 20 g (0.1 mol) o f bromide 8b. Compound 18 was purified by distillation, bp 82-83 "C (9 mm), ~? O D 1.4521 [lit.29 bp 59-61 "C (5.5 mm), n20D 1.45203. Ethyl-3,3-dimethylcyclohexanone (19). By the above procedure compound 19 was formed in 62% yield from 4 g (0.026 mol) of chloride 13 and was purified by distillation, bp 86 "C (6 mm), n 2 5~ 1.4556. 2-T h e reduction o f the acetylenic epoxides 9 w i t h lithium in liquid ammonia leads t o the selective cleavage of the propargyl oxygen bond and produces a mixture o f cisand trans-2-ethynylcycloalkanols. The 5-ethynylcycloalkanols can be oxidized t o 2-ethynylcycloalkanones which are useful substrates for photochemical ring expansions.

Auf dem im Formelschema angegebenen Weg werden die cyclischen Ketone (I) in die Epoxide (V) übergeführt, die nach Umwandlung mit Methyllithium in die entsprechenden Acetylide (Schutz vor Überreduktion) mit Lithium in flüssigem Ammoniak in selektiver Weise zu den Äthinylalkoholen (VI) und ( VII) gespalten werden.

Die Belichtung des Methyl‐cyclopentenyl‐eyclopentanons (I) bei Å = 300 nm ergibt in Hexan den Bicyclus (II), der durch Behandlung mit p‐Toluolsulfonsäure in Benzol zur Verbindung (III) isomerisiert.