Cycloheptane annelation

Cycloheptane annelation.1 A new route to cycloheptanes is based on a Lewis acid-catalyzed, intramolecular addition of an allylsilane group to a 3-vinylcycloal-kenone (equation I). This annelation has been applied to a synthesis of the ses-... 

Cycloheptane annelation (7, 212). The mixed cuprate 1 reacts with acid chlorides to afford vinylcyclopropyl ketones. Previously these ketones were prepared from aldehydes by condensation with l-lithio-2-vinylcyclopropane followed by oxidation (7, 192-193). These compounds are rearranged to 4-cycloheptenones on conversion to trimethylsilyl enol ethers, thermolysis, and hydrolysis. ... 

Cycloheptane derivatives (7, 192-193). Wender et a/. have applied their cycloheptane annelation procedure to total syntheses of the pseudoguaianolides damsinic acid (1) and confertin (2). The paper describes the synthesis of 1-lithio-l-methyl-2-vinylcyclopropane, which is the annelation reagent utilized in the pseudo-guaianolide syntheses. 

Cycloheptane annelation. The method cited above has been extended to the synthesis of jS-(2-vinylcyclopropyl)enoncs. The cuprate for this purpose is lithium... 

Cycloalkenones, 153 Cyclobutadiene, 55-56 Cyclobutanol, 6-7 Cyclobutanone, 6-7 Cyclobutanones, 68, 387 Cyclobutenes, 146 Cyclocarbonylation, 278 3a,5o -Cyclocholest-7-ene-6-ol, 70 7-Cyclodtral, 92 Cyclodehydration, 32 Cyclododecanone, 297 Cycloheptane annelation, 212 4-Cycloheptene-4-ones, 192 1,3-Cyclohexadienes, 63... 

Additionally, benzoannelated cycloheptanes 54 were obtained in good yields (Scheme 18). It was also possible to extend the methodology to dis-ubstituted or benzoannelated iodo arenes as substrates, giving rise to the formation of various functionalized annelated cyclohexanes and cyclohexanes 55-61 (Scheme 19). 

Benzene annelation significantly increases the barrier to ring inversion processes. Saturated seven-membered rings can invert by pseudorotation (pseudorotation barrier is 2 kcal/mole) which has not been measured by NMR techniques. The AG for the ring inversion process for the benzene-annellated derivatives of cycloheptane (which probably exists in a chair form) was determined to be 10.9 kcal/mole at Tj, = — 57°C (186, 298, 322). Equilibria in tricyclic organic derivatives have been studied more extensively. Several different inversion processes have been reported and depend on structural type. The following are examples of ring inversion processes. 

Cycloheptane derivatives. Annelated cycJohepfane derivatives have been prepared by reaction of (1) with 3-alkoxyenoncs to form 1,2-divinylcyclopropanes (2), which rearrange thermally to annelated cycloheptadiene derivatives (3) (equation I). Actually, either trans- or rts-(l) or a mixture of the two can be used since both cis- or trans- 2 rearrange on thermolysis to the same product (3), although trans-(2) requires somewhat more drastic conditions. The overall yield of (3) using a 7 3 mixture of cis- and trans-i ) is 2 7o ... 

---