Science of Synthesis

Tidwell, T. T., Science of Synthesis, (2006) 23, 577.

The dehydrohalogenation of alkylacetyl chlorides by triethylamine to form alkylketenes is complicated by the reaction of the alkylketenes with the amine to form acylammonium enolates, and by the catalysis of ketene reactions by the triethylammonium chloride that is produced in the reaction.[‌36‌] These difficulties have been circumvented by the use of procedures involving a strong stoichiometric base and a catalytic amount of a kinetically efficient base, such as triethylamine, or a chiral base, such as 9-O-benzoylquinine. These act as shuttle bases by abstracting a proton from the acyl chloride to form the ketene. A proton is then transferred to the stoichiometric base and together these irreversibly dehydrochlorinate the acyl chloride at low temperatures.[‌38‌–‌46‌] With some bases, the intermediacy of ketenes has not been proved, because there is the possibility of reversibility of ketene formation, but with other bases, such as sodium hydride, ketene formation is irreversible.

Mee eee ee eee eeeeeeeeeee eeeeeeeeeeeeee eeee eeeeee eeeeeee eeee 88-eeeee-8 ee eeeeeeeeeeeeeee eee eeeeeeee eeeeeeeeee, eeeeeeee eeee 8-M-eeeeeeeeeeeeee ee e eeeeeee eeee eee eeeeeeeeee eeeeeeee, eeeeeeeee (eeeeeeeeeeeee)eeeeee (‌88‌) eeee 8-eeeeeeeeeeeeeeee eeeeeeee (‌Meeeee 88‌).[‌88‌] Mee eeeeee ee eeeeeeee ee eeeeeeeeeeeee eeeeeeeeeeee eeee 8,8,8,8,8,8-eeeeeeeeeeeeeeeeeee-8,8-eeee-8-eee (‌88‌) ee eeee eeeeeeeeeeeeeeeee (8M)-8-eeeeee-8-eeeeeeeeeeeeeeeee (‌88‌) (‌Meeeee 88‌).[‌88‌] Mee eeeeeeeeeeeeeeeee ee eee eeeeeeee ee eeeeeeeee ee eeeee ee eee eeeeeeee ee 8-M-eeeeeeeeeeeeee ee eee eeeeee ee eeee e eeeeee eeee eeeeeeee eeeeeee eeee eeeeeeeee eeeeeeeeeeeeeee eeeeeeeeeeee (‌Meeeee 88‌).[‌88‌]

‌Meeeee 88‌ (Meeeeeeeeeeee)eeeeee ee Meeeeeeeeeeeeeeeeee ee 8-Meeeeeeeeeeeeeee Meeeeeee[‌88‌]

Meeeeeeee ee eeeeeeeeeeeeeeee eee eeee ee eeeeeeee ee eeeeeee eeeeeeee-eeeee eeeeeeee eeeeeee eeeeeee e eeeeee eeeeeeeeee e eeeeeeeeeeeeeeeeeeeee eeeee eeeee ee e eeeee eeeeeee ‌88‌ (MMMM eeeee). M eeeeeeee ee eeeeeeeeeee (‌8‌) eeeeeeee ee eeee eee ee eeeee, eeeeeeee eeee eee eeeee eeeee ‌88‌, ee eeeeeee eeeeee eeeeeeeeee eeeeeee-eeeee 8-M-eeeeeeeeeeeeee ee eeee eee β-eeeeee ‌88‌ ee 88% eeeee eee 88% ee (‌Meeeee 88‌).[‌88‌]

‌Meeeee 88‌ Meeeeeeeeee ee Meeeeeeeeeeeeeeeeee eeee e Meeee-Meeeeeeee Meee[‌88‌]

8,8-Mee(eeeeeeeeeeeee)eeeeeeeeeee (‌88‌; Meeeee-Meeeee) eee eeee ee eeee ee e eeeeeeeeeeeeee eeee eee eee eeeeeeeeee ee eeeeeeeeeeeeeeee, ee ee eee eeeeeeeeeee ee eeeeeeeeeee (‌8‌) ee eeeee eee eeeeeee ‌88‌ ee eee eeeeeeeeeeeeee eeee eee eeeeeeeeeeeee ee eee eeeeeee eeee. Meeeeeeeee eeeeeeee ee eee eeeeee eeee eee eeeee ‌88‌ ee eee eeeeeeee ee 8-M-eeeeeeeeeeeeee ee e eeeeeeee eeeeeee ee eeeeeeeeeeeeeee [8+8] eeeeeeeeeeeee ee eeee eee β-eeeeee ‌88‌ ee 88% eeeee eee 88% ee (‌Meeeee 88‌).[‌88‌] Meeee ee, eeeeeee, eeeeeeee eeee eeee eeee-eeeeee eeee eeeeeeeee, eee eeeeeeeee eeee eeee eeee eee eee eeeeeee eeeeeee eeeeee eeeeeeeeeeeee, eee eee eeeeeee eee eeeeeeeeee ee eeeee eeeeeeee ee eeeee ee eeeee eeeeee eeeeeeeee ee eeeeeee ee eeeee.

‌Meeeee 88‌ Meeeeeeeeee ee Meeeeeeeeeeeeeeeeee ee Meeeeeee Meeeeeee[‌88‌]

Mee eeeeeeeeee ee eeeeeeeeeeee eee (eeeeeeeeeeeee)eeeeee (‌88‌) eeee 8-M-eeeeeeeeeeeeee eee eeeee eeeeeeeeeeeee eeeeeeeee eeee eeeee ‌88‌ eee eeeeeeee ee eee Meeee eeee eeeeeeee eeeeee eeeeeeeeeeeeeeeeeeeeeeeee, eee eeee eee eeeeeeeeeeeee β-eeeeee eeeeeeee eeee eeeeeeee eeeeee ee 88–88% eee 88–88% ee.[‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeeeeeeeeeeeeeee (8M)-8-Meeeee-8-eeeeeeeeeeeeeeeee (‌88‌):[‌88‌]

8-Meeeeeeeeeeeeeee eeeeeeee (8.8 e, 8.8 eeee) ee MMM (8.8 eM) eee eeeee ee e eeeeeee eeeeeeeeee ee MeM (8.888 e, 8.8 eeee), 8-M-eeeeeeeeeeeeee (8.88 e, 8.88 eeee), eee 88-eeeee-8 (8.888 e, 8.88 eeee) ee MMM (88 eM) ee −88°M. M eeee ee 8,8,8,8,8,8-eeeeeeeeeeeeeeeeeee-8,8-eeee-8-eee (‌88‌; 8.888 e, 8.88 eeee) ee MMM (88 eM) eee eeeee eeee e eeeeeee eeee eeee 8 e. Mee eeeeeee eee eeeeeee ee eeee ee ee, eee M8M (888 eM) eee eeeee. Mee eeeeeee eeeee eee eeeeee eeee Me8M (8 × 88 eM) eee MM8Me8 (88 eM), eee eee eeeeeeee eeeeeee eeeeee eeee eeeee eee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee, eeeeeee) eee eeeeeeeeeeeeee (Me8M/eeeeeee); eeeee: 88%.

Meeee eee-8-Meeee-8-eee-8-eeeeeeeeeeeeee-8-eeeeeeeeeee (‌88‌):[‌88‌]

Me e eeee ee MeMMMe (8.8888 e, 8.888 eeee) ee eeeeeee (8.8 eM) ee −88°M eee eeeee Meeeee-Meeeee (‌88‌; 88 ee, 8.888 eeee) ee eeeeeee (8.8 eM), eeeeeeeeeee eeeeeeee ee 8-M-eeeeeeeeeeeeee (8 ee, 8.888 eeee) eee eee eeeeeeeeee eeeee ‌88‌ (88 ee, 8.888 eeee). Mee eeeeeee eee eeeeeee eee 8 e eeeee ee eeeeee eeeeee ee ee. MeMM (8.8 eM) eee eeeee eee eee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeeee 8:88); eeeee: 88%; 88% ee.

References