2-CYCLOHEPTEN-l-ONE

Cyclohepten-l-one has been prepared from cycloheptanone by dehydrohalogenation of the ethylene ketals of 2-chloro- and 2-bromocycloheptanone and subsequent hydrolysis. The a,)3-dehydrogenation of cycloheptanone has also been effected via the... 

ONE-CARBON RING EXPANSION OF CYCLOALKANONES TO CONJUGATED CYCLOALKENONES 2-CYCLOHEPTEN-l-ONE... 

Diels-Alder reactions continue to be of value for the interception of highly reactive dienes or dienophiles. Thus, irradiation of 2-cyclo-octen-l-one or of 2-cyclohepten-l-one in the presence of excess cyclopentadiene affords the norbornene derivatives (173 n = 5 or 4 respectively), which undergo retro-[4 -I- 2] addition on distillation. Presumably the trans-2-cycloalken-l-ones are reactive intermediates in these processes. Elimination of acetic acid from bis(trifluoromethyl)cyclopentadienylcarbinyl acetate yields the reactive 6,6-bis(trifluoromethyl)fulvene, which rapidly dimerizes by [4 + 2] cycloaddition the fulvene intermediate can be intercepted by similar addition to cyclopentadiene. The adduct (174) is formed on reaction of cyclopentadiene with the imine produced by iodine-catalysed rearrangement of NN-... 

Ring Expansions. Trost first demonstrated the advantages of methoxy(phenylthio)methane over bis(phenylthio)methane as an acyl anion equivalent in a synthesis of a-methylene-5-lactones via the ring expansion of y-butyrolactones (eq 10). Use of the 0,S-acetal reagent avoided problems encountered with enoliza-tion. Methoxy(phenylthio)methane has also been utilized for the ring expansion of nonenolizable 2-/j-butylthiomethylene cyclohexanones to 3-formyl-2-cyclohepten-l-ones (eq 11). ... 

An ice-cooled soln. of ethyl 4-pentanonylacetoacetate in benzene satd. with dry HCl, allowed to stand 10 hrs., poured on ice, and the crude intermediate heated 3 hrs. at 135-140° with an equal quantity of dimethylaniline 3-methyl-7-carbethoxy-2-cyclohepten-l-one. Y 60%. H. Jager and R. Keymer, Arch. Pharm. 293, 896 (1960). 

A soln. of m-2-cyclohepten-l-one and a 20-fold amount of isoprene in hexane irradiated 1 hr. with the Pyrex-filtered light of a 100 w. medium-pressure Hg-lamp -> product. Y 95%. F. e. s. H. Shinozaki, S. Arai, and M. Tada, Bull. Chem. Soc. Japan 49, 821 (1976). 

With the multifunctional primary amine-thiourea catalyst (which was prepared from (l/ ,2/ )-l, 2-diaminocyclo-hexane and 9-amino (9-deoxy) epiquinine) in the absence of additives, the asymmetric Michael addition of malonate to cyclic enone proceeded well to afford 1,4-adducts in excellent yields and enantioselectivities (Table 9.10). Particularly noteworthy is that all examined malonates afforded higher than 95% enantioselectivities. In general, the reaction could even complete within a short period of time (12-18 hours) to give >90% yields and high enantioselectivity (93-96% ee) when the reactions were carried out at an elevated reaction temperature. Moreover, the reaction of 2-cyclohepten-l-one also afforded more than 90% ee and 83% yield. Furthermore, the use of 4,4-dimethylcyclohex-2-enone resulted in 77% yield with 91% ee. Only 2-cyclo-penten-l-one furnished medium yield and enantioselectivity. In contrast to previous reports, this reaction system exhibits excellent catalytic activity in asymmetric Michael addition with a broad scope of both malonate and cyclic enone. 

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