Science of Synthesis

von Angerer, S.; Warriner, S. L., Science of Synthesis, (2007) 29, 373.

Acetals are capable of adding across the C=C bond of alkoxyethenes to give new acetals with a chain length extended by two carbon atoms. This addition reaction is catalyzed by a variety of Lewis acids[‌248‌,‌546‌–‌553‌] and the acidic montmorillonite K 10 clay (‌Scheme 106‌).[‌554‌] In the course of the reaction, one of the alkoxy groups of the reacting acetal ‌97‌ becomes part of the new acetal structure ‌98‌, whereas the other remains at the original carbon atom. Hydrolysis and subsequent elimination of the remaining alkoxy group as an alcohol give rise to the formation of trans-α,β-unsaturated aldehydes. This reaction also works with 1-alkoxybutadiene and isoprenyl building blocks to give the products of 1,4-addition, but the yields are only moderate.[‌551‌,‌555‌] Diacetals of dialdehydes, e.g. terephthalaldehyde or 1,1,4,4-tetramethoxybut-2-ene, undergo the same reaction and permit the simultaneous extension in two directions.[‌552‌,‌553‌,‌556‌] This method has been used for the preparation of vitamin A aldehyde and its congeners.[‌550‌]

‌Meeeee 888‌ Meeee Meeeeeeee ee Meeeeee ee Meeeeeee eeee Meee Meeeee[‌888‌–‌888‌,‌888‌,‌888‌]

‌Meeeeeeeeee 888‌

M8	M8	M8	M8	Meeeeeee	Meeee (%)	Mee
Me	M	Me	M	MeMe8	88	[‌888‌]
(MM8)8		Me	M	MeMe8	88	[‌888‌]
Me	M	Me	Me	MM8•MMe8	88	[‌888‌]
MM=MMMe	M	Me	M	MeMe8, MeMM	88	[‌888‌]
Me	M	Me	M	eeeeeeeeeeeeeee M 88	88	[‌888‌]
	M	Me	MMe=MM8	MeMe8, MeMM	88	[‌888‌]

Meeeeeeeeeee Meeeeeeee

8,8,8-Meeeeeeeeeeeeeee (‌88‌, M8 = M8 = Me; M8 = M8 = M); Meeeeee Meeeeeeee:[‌888‌]

Meeee eeeee eeeee (88 e, 8.88 eee) eee eeeee eeee 8.8–8 e ee e eeeeeeeeee ee eeeeeeeeeeeeeee M 88 eeeeeeee (8.8 e) ee 8,8-eeeeeeeeeeeeeee (‌88‌, M8 = M8 = Me; M8 = M; 888 e, 8.8 eee), eeee eee eeeeeeeeeee ee eee eeeeeee eeeeeeeeee ee 88–88°M. Meee eee eeeeeeee eee eeeeeeee, eeeeeeee eee eeeeeeeee eee ee eeeeeeeeee 88 eee ee 88°M. Mee eeeeeee eee eeee eeeeeeee eeeeeee e eeeeeeee eeeee eeeeee eee eeeeeeeee eeee M8MM8 eeeeeee e eeeee-eeeeee 88-ee Meeeeee eeeeee. Mee eeeeeeeee eeeeee (88 e, 8.88 eee) eee eeeeeeeee eeeee ee eeeeeeeeeee eeeeeeee, eeeeeeee ee eeeeeeeeeeee ee eee eeeeeee eeeee eeeeeee eeeeeeee; eeeee: 88.8 e (88%); ee 888°M/88 Meee.

References

Meeeeee Meeeeeeeeee

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