Science of Synthesis

Kostikov, R. R.; Khlebnikov, A. F.; Sokolov, V. V., Science of Synthesis, (2010) 47, 824.

The classical Hofmann alkene synthesis from alkylamines (or from alkyl halides) includes the preparation of a quaternary ammonium hydroxide ‌88‌ and its pyrolysis at 105–150°C. Frequently, the ammonium hydroxides are obtained by reaction of the respective ammonium salts with silver(I) oxide, barium oxide, or ion-exchange resins in situ without isolation of the hydroxide as a pure compound. The reaction proceeds by proton abstraction from an α-carbon position by the hydroxide anion to give an intermediate ammonium ylide. The latter then undergoes an intramolecular fragmentation to an alkene molecule and a tertiary amine. The transition structure ‌89‌ of the elimination is a five-membered ring, and the process is a syn elimination (‌Scheme 34‌) (see also Houben–Weyl, Vol. 5/1b, pp 219–235).[‌192‌]

‌Meeeee 88‌ Meeeeeeee eee Meeeeeeeeee β-Meeeeeeeeee eeee Meeeeeeeeeeeeeeeeeeeee Meeeeeeeee

Mee eeeeeeeeeeeeeeee ee eee eeeeeeeeeee eeeeeeeeeee ee eeee eeee eee eeeeeeeeeeeee eeeeee eeeeee eee e eeeeeee eeeeee ee eeeeeeeeeeee ee eee eeeeee eeee (Meeeeee eeee). Meeeeeeee, eeee eeeeee ee eeeeeee eeee eee eee eeeeeeeee ee eee-8-eeee eee 8,8-eeeeeeeeeeeee eeeeeee (‌Meeee 88‌).[‌888‌–‌888‌]

‌Meeee 88‌ Meeeee Meeeeeeee ee Meeeeeeeeee ee Meeeeeeeeeeeeeeeeeeeee Meeeeeeeee[‌888‌–‌888‌]

Meeeeeee Meeeeeee	e	Meeeeee(e)	Meeee (%)	Mee
	–		88	[‌888‌]
	8		88	[‌888‌]
	8		88	[‌888‌]
	8		88	[‌888‌]
	8		88	[‌888‌]
	8		88	[‌888‌]
	8		88	[‌888‌]
	8		88 + 88	[‌888‌]
	8		88 + 88	[‌888‌]
	–		88 + 8 + 88	[‌888‌]
	–		~88 + 88–88	[‌888‌,‌888‌]

References

Meeeeee Meeeeeeeeee

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