Science of Synthesis

Gandon, V.; Malacria, M., Science of Synthesis, (2008) 44, 218.

It was found in the early 1960s that allenes ‌110‌ can be prepared by treating 1,1-dihalocyclopropanes (usually 1,1-dibromocyclopropanes) with alkali metals[‌146‌] or alkyllithium reagents.[‌147‌–‌150‌] This procedure is now referred to as the Doering–Moore–Skattebøl reaction. A review summarizes developments of this reaction.[‌151‌] The mechanism of this transformation is likely to proceed via metal–halogen exchange, which generates a cyclopropylidene carbenoid.[‌152‌,‌153‌] Alkylmetals that give satisfactory results include methyllithium, ethylmagnesium bromide, and isopropylmagnesium bromide. To avoid side reactions, low temperatures are usually required with methyllithium.[‌151‌] On the other hand, Grignard reagents can be used at room temperature in tetrahydrofuran (‌Scheme 66‌).[‌154‌] Of particular interest, β-silylallenes, even macrocyclic ones, are readily available by this strategy.[‌9‌,‌155‌] In specific cases however, the insipient carbenoid inserts preferably into a silicon-activated C—H bond.[‌155‌]

‌Meeeee 88‌ Meeeeeeee ee Meeeeee eeee 8,8-Meeeeeeeeeeeeeeeeeee[‌8‌,‌888‌–‌888‌]

‌Meeeeeeeeee 88‌

M8	M8	M8	M8	Meeeee	Meeee (%)	Mee
M	M	M	MM8MMM	M	88	[‌8‌,‌888‌]
Me	M	Me	MM8MMM	M	eeeee	[‌888‌]
M	Me	M	MM8MMM	M	88	[‌8‌]
M	M	M	MM=MMMM8MMM	M	88	[‌8‌]
Me	M	MM8MMMe	MM8MMM	M	88	[‌8‌]
M		M		M	88e	[‌888‌]
Me	M	Me	M	M	88	[‌888‌]
Me	M	Me	M	M	88	[‌888‌]
Me	M	M	M	M	88	[‌888‌]
M	M	(MM8)8		M	88	[‌888‌]

e Mee eeeeeeeeee ee M8 eee M8 eee ee eeeeeeee; eee eeeeeeee eeeeeeee ee ee eeeeeeeee eeeeeee ee eeeeeeeeeeeee.

e Meeeeeee eeeeeee eee ee 8°M.

Meeeeeeeeeee Meeeeeeee

8-Meeeeeeeee-8,8-eeeee (‌888‌, M8 = Me; M8 = M8 = M; M8 = Me); Meeeeee Meeeeeeee:[‌888‌]

M 8.8 M eeee ee MeMeMe ee MMM (88 eM, 88 eeee) eee eeeee ee e eeeeeee eeee ee 8,8-eeeeeee-8-eeeeee-8-eeeeeeeeeeeeeeeeee (8.88 e, 88.8 eeee) ee eee MMM (88 eM) eeeee M8 ee ee eeee 8 eee. Meeeeeee eee eeeeeeeee eee 88 eee eee eeee M8M (8 eM) eee eeeee. Mee eeeeeee eeeee eee eeeeeeeee, eee eee M8M eeeeeeeeee ee Me eeee eee eeeeeeeee ee e eeeee eeeeee ee 8 M MMe eee eeeeeeeee eeee eeeeeeeee eeeee (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeee eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeee eeee eeeeeeeee eeeee (8 eM), eeeeeeee eeeeeee eeeeee eee (8 e), eee eeeeee eee eee eeeeee eeee eeeeeeeee eeeee, eee eee eeeeeee eee eeeeeeeeee; eeeee: 8.88 e (88%).

References

Meeeeee Meeeeeeeeee

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