The formation of cycloheptenone and cycloheptadienones from bicyclo[3.2.0]heptanone derivatives. An acid-catalyzed, two carbon ring expansion reaction

Abstract

In strong acids, such as FSO3H and 96% HzS04, bicyclo[3.2.0]heptan-6-one and bicyclo-[3.2.0]hept-2-en-7-one undergo a clean isomerization to form protonated cyclohept-2-enone and cyclohepta-2,4dienone, respectively. Substituted derivatives undergo comparable ring expansions when dissolved in these strong acids. The seven-membered ring ketones can be recovered on quenching the acid solutions with a NaHCO3-ether mixture. In contrast, bicyclo-[3.2.0]hept-2-en-6-one when dissolved in FSO3H rearranged to give protonated l-acetylcyclopentadiene. The mechanism and synthetic utility of these reactions is discussed. KENNETH E. HINE et RONALD F. CHILDS. Can. J. Chem. 54, 12 (1976).Dans les acicies forts comme FSO3H et HlS04 96y0 la bicyclo[3.2.0]heptanone-6 et la bicyclo[3.2.0]heptkne-2 one-7 subissent des isornerisatio~~s propres conduisant respectivement aux formes protonCes de la cycloheptkne-2 one et de la cycloheptadikne-2,4 one. Des derives portant des substituants subissent des extensions de cycle comparables lorsque dissous dans ces acides forts. On peut rCcupCrer les cCtones cycliques a sept chainons en traitant les solutions acides par un melange NaHCOs-Cther. Par ailleurs le traitement de la bicycIo[3.2.O]heptkne-2 one-6 par FSO3H conduit k la forme protonee de l'acetyl-1 cyclopentadikne. On discute du mecanisme et de l'utilite en synthiese de ces reactions.[Traduit par le journal]There are numerous examples of fused bicyclic ring systems in which one of the rings is a cyclobutanone moiety. Indeed, one common and facile synthetic entry into this type of ring system involves the cycloaddition of a ketene to a cycloalkene (I). If a means could be found of inducing cleavage of the cyclobutanone bond that is conunon to both rings, then combined with this ketene addition, we would have a route t o functionalized monocyclic systems possessing a ring two carbons larger than that of the alkene used in the original cycloaddition. A viable two carbon ring expansion reaction would be of value in general syntheses of medium size rings (2). The well known interconversion of cyclobutyl, cyclopropylcarbinyl, and open chain cationic systems (3) suggested t o us that one method of inducing the desired cleavage of the cyclobutanone bond would be to react this carbonyl function with an electrophile. There are several reports of the isomerization of cyclobutanones upon protonation and it would appear that in nlany of these rearrangements the carbon-carbon bond / 3 to the carbonyl group is cleaved (4). In view of our interest in the chemistry of the monocyclic, unsaturated, seven-membered ring ketones (5), we have examined the effect of protonation on several bicyclo[3.2.0]heptan-6-ones and bicyclo[3.2.0Jheptenones and report here the results of this study. ResultsCareful solution of bicyclo[3.2.0]heptan-6-one, 1, in FS03H at -78 "C yielded a clear yellow solution whose pmr spectrum at +20 "C (

Preparation of TADOOH, a Hydroperoxide from TADDOL, and Use in Highly Enantioface- and Enantiomer-Differentiating Oxidations

“…Bicyclo[4.2.0]octan-7-one [56] and exotricyclo[4.2.1.0 2,5 ]nonan-3-one [57] were obtained from the corresponding olefins (cyclohexene and norbornene ( bicyclo[2.2.1]hept-2-ene)) by [2 2] cycloaddition of dichloroketene (generated in situ from Cl 3 CCOCl and Zn powder, with ultrasound activation, according to literature procedures [58]), followed by dechlorination (Zn powder and AcOH [59]). Bicyclo[3.2.0]heptan-6-one [60] was obtained from bicyclo[3.2.0]hept-2-en-6-one by catalytic hydrogenation (H 2 , atmospheric pressure, 10% Pd/C, AcOEt [34]). All long-time reactions at À 788 were carried out using a Lauda Ultra Kryomat RUK90, all long-time reactions at À 308 with a Frigomix S. 2.…”