Cyclopropenes catalytic hydrogenation

Catalytic hydrogenation of 29 on the other hand is in full agreement with the rules of Musso That means all three bridging a-bonds of the three-membered rings are opened to yield 1,1,4,4,7,7-hexamethylcyclononane as the only product Catalytic 2 1 -cotrimerizations between cyclopropenes and alkenes as well as alkynes are also known. It has already been mentioned (see Chap. 2.2.1) that a nickel(O) catalysts — modified by the bulky phosphane P(iPr)2(rBu) — favors the cocyclotri-merization of 3,3-dimethylcyclopropene and methyl acrylate (Eq. 41). 

Occasionally, gew-dichlorocyclopropanes with phenyl or alkoxy substituents are transformed by strong base in aprotic or (rarely) protic solvents to allylic substitution products that do not obey at all the rules for cyclopropyl to allyl rearrangements with regard to their constitution and configuration. "These reactions are mechanistically distinct. They are usually initiated by base-induced elimination of hydrogen chloride to form phenyl- or alkoxy-substituted cyclopropenes, which are then intercepted by nucleophiles. ° These reactions are discussed in Section 2.B.2.I. Small structural differences can divert the reaction into one or the other reaction channel. Cyclopropane 25 on treatment at — 50°C with 2 equivalents of potassium /er/-butoxide in tetrahydrofuran in the presence of catalytic dicyclohexano-18-crown-6... 

---