Science of Synthesis

Krueger, A., Science of Synthesis, (2008) 43, 534.

The rearrangement of a cyclopropylcarbene also proceeds over a coarctate transition state. Concerning the complexity of the transition state, the fragmentation of cyclopropylcarbenes is among the simplest examples for coarctate reactions. It has been well studied since its discovery in 1960.[‌267‌] It leads to the respective pair of an alkene and an alkyne in the case of monocyclic starting compounds ‌158‌ and to linear enynes in the case of bicyclic starting compounds (‌Scheme 74‌).[‌263‌] Fragmentation is favored over ring expansion in the case of five-, six-, and seven-membered rings bridging the cyclopropyl ring. This is due to the fact that these ring sizes lead to exclusive endo arrangement of the cyclopropylcarbene. Larger rings allow for more steric flexibility.

‌Meeeee 88‌ Meeeeeeeeeeee ee Meeeeeeeeeeeeeeeeee[‌888‌]

Mee eeeeeeee eeeeeeee eee ee eeeeeeee ee eeeeeeeee eeeeeee. Me eeee eeeee eee eeeeeeeeeeeee ee eee eeeeeeeeee eeeeeeeeeeeeee eee e eeeee eeeeeeee ee eeee ee eeeeeeee eee eeeeeee (‌Meeee 88‌).[‌888‌–‌888‌]

‌Meeee 88‌ Meeeeeeee ee Meeeeee ee Meeeeeeeeeeee ee Meeeeeeeeeeeeeeeeee[‌888‌–‌888‌]

Meeeeeee	Meeeeee	Meeeeeeeee	Meeeee (%)	Mee
		MeMMe, eeeeeee, 888°M	88	[‌888‌]
		MeMMe, 888–888°M, 8.8 Meee, 8.8 e, eeeeee eeee (−88°M)	88	[‌888‌]
		MeMMe, eeeeeee, 888°M eeeeeee, 888°M 888°M	8.8e 88e 88	[‌888‌] [‌888‌] [‌888‌]
		888°M	88	[‌888‌]
		888°M	88e	[‌888‌]
		8. MeMM, MeMMe 8. Meeeee, 888°M	88	[‌888‌]
		8. MeMM, MeMMe 8. Meeeee, 888°M	88	[‌888‌]
		8. MeMM, MeMMe 8. Meeeee, 888°M	88	[‌888‌]
		888°M, 8.8 Meee, 8 e, eeeeee eeee (−88°M)	88	[‌888‌]
		888°M, 8.8 Meee, 8.8 e, eeeeee eeee (−88°M)	88	[‌888‌]
		eeeeee eeeeeeeee, 888°M	88	[‌888‌]
		MeMMe, eeeeeeeeee, 888°M	88	[‌888‌]
		888–888°M, 8.8 Meee, eeeeee eeee (−88°M)	88	[‌888‌]
		888–888°M, 8 Meee, eeeeee eeee (−88°M)	88	[‌888‌]
		MeM, eeeeeee, 888°M	88e	[‌888‌]
	MM≡MMM8Me	eeeeeee, Meeee eeee, eeeeee-eeeeeeee Me eeee, 8 e, eeeeeeee eeee eeeeeee eeee ee −88°M	e.e.	[‌888‌]
	MM≡MMM8Me	Meeee eeee, eeeeeee, eeeeee-eeeeeeee Me eeee, 8 e, eeeeeeee eeee eeeeeee eeee ee −88°M	e.e.	[‌888‌]
	MM≡MM	Meeee eeee, eeeeee-eeeeeeee Me eeee, 88 Meee, 8 e	88	[‌888‌]
		eeeeeeeeeee MM, eeee	88e	[‌888‌]

e e.e. = eee eeeeeeee; eeee eee-8-eee ee eee eeeeeeeeeeeee eeeeeeee eee eeeeeeee.

e Me eee eeeeeeee ee eeee eee eeeee eeeeeeeeee ee eee eeeeee eee eeeeeeeeee.

e Mee MM8Me eeeee ee ee eee eee-eeeeeeee; eee eeeee eeeeeee ee eee eeeeeeee ee eeeeeeeeeee ee eee eeeeeeeeeee eeeeeeeeee.

e Meeeeeee eeeeeeeee eeeeeeee ee eee eeeeeeeeeeee eeee ee eee eeeee,[‌888‌] eee eeeeeeeee eeeeeee eee eee eeeeeeeee eeeee.

e MM eeeee.

Meeeeeeeeeee Meeeeeeee

8,8-Meeeeeeeeee-8-ee-8-eee (‌888‌); Meeeeee Meeeeeeee:[‌888‌]

Mee Me eeee ee eeeeeeeeeeeeeeeeee eeeeeeeeeeeeee eee eeeeeeee eeee eee eeeeeeeeeeeeee (8.8 e, 88 eeee) eeeeeeeee ee eee eeeeeee eeeeee ee MeMM (8 eM) ee eeeeeeee ee MeMMe (8.88 e, 88 eeee). Meee eeeeeee eee eeeeee ee 88–88°M eee eeeeeeee MeMM eee eeeeeee ee eeeeeee eeeeeeee eeeeeeeee. Mee eeeeeeeee eeeee eee eeeee eeee ee eeeee eeeeee ee Meeeee eee eeee eeeeee eeeeeee eee eeeeee ee 888°M ee eeeeeee eeeeeeee (8 Meee). Mee eeeeeeee eeeeeeeee eeee eeeeeeeee ee e eeeeee eeee (eeeeee eeee eee eee/MeMM). Mee eeeeeee eeeeeee eee eeeeeeeee eeeee eeeeeeeeeee MM (8% MM-88 ee Meeeeeeeee M, 88°M). Mee eeeee eeeeeee (88%) eee eeeee ee ee eee eeeeeeeeeee eeeeeee eeeeeeeeeee. Mee eeeee eeeeeeee eee eeeeeeeeee ee eeeeee ‌888‌; eeeee: 8.88 e (88%); 8M MMM (MMMe8, δ): 8.88 (e, 8M), 8.8 (e, 8M), 8.88 (e, 8M), 8.88 (e, 8M).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8e, 888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.
• 8.Meeeee-Meee, (8888) M 88e8, 888.