Carbon-Carbon Bond Fission in Cyclopropanes. IV. The Acid-Promoted Opening of the Three-Membered Ring in exo-7-Methylbicyclo [4.1.0]heptane and exo-6-Methylbicyclo [3.1.0]hexane

d0/fn-Mediated Ring-Opening Ziegler Polymerization (ROZP) and Copolymerization with Mono- and Disubstituted Methylenecyclopropanes. Diverse Mechanisms and a New Chain-Capping Termination Process

“…This is not surprising, since the cationic rearrangement of the norcarane structure has ample literature precedent . In one particular example involving the acid-promoted cationic rearrangements of bicyclo[4.1.0]heptane and 7-methylbicyclo[4.1.0]heptane, it was reported that product formation followed both pathway A (∼23%, eq 10) and pathway B (∼77%, eq 10) for bicyclo[4.1.0]heptane (R = H, eq 10) . Similarly for 7-methylbicyclo[4.1.0]heptane (R = CH 3 , eq 10), ∼53% follows pathway A and ∼47% pathway B (eq 10) .…”

“…33 Similarly for 7-methylbicyclo[4.1.0]heptane (R ) CH 3 , eq 10), ∼53% follows pathway A and ∼47% pathway B (eq 10). 33 Therefore, it seems almost certain that the carbocations present in a cationic polymerization of monomer B would undergo ring opening. Indeed, as noted above, numerous isomers of B are detectable in the supernatant GC/MS during the cationic polymerization of B (all B is consumed; none is detectable by GC/MS).…”

Ring-opening of some radicals containing the cyclopropylmethyl system

“…Treatment of the ketone (36) with tributylstannane followed by methanolysis of the initial products afforded the compounds (38), (40), and (42) in yields given in the Scheme, which also shows the mechanism.21 The fact that the major rearrangement product is the ketone (40) demonstrates that the radical (37) preferentially undergoes ring-opening by fission of the less substituted Pybond to afford the less stable possible product radical (39). Similarly, the radical (43), generated by treatment of the alcohol (38) with di-t-butyl peroxide afforded the ketone (36) and the two rearrangement products (40) and (42).…”

“…Treatment of the toluene-p-sulphonate of the alcohol with lithium chloride in hexamethylphosphoric triamide gave the same result. (38) .-Norborn-5-en-2-one 42 was converted as previously described 43 into the required alcohol, b.p. 82-83 "C at 8 mniHg, which was shown by g.1.c.…”

“…Reaction of l-Methylnortricyclen-3-01 (38) with Di-t-butyl Peroxide.-A mixture of the alcohol (150 mg) and the peroxide (25 mg) was heated in a sealed tube a t 140 "C for 24 h. The products (95%), determined by g.1.c. [column (f), 150 "C] were : 1-methylnortricyclen-3-one (67%), 4-methylnorbornan-2-one ( 17 yo), and 5-methylnorbornan-2-one E.s.r.…”