Science of Synthesis

Härtinger, S.; Härtinger, M., Science of Synthesis, (2007) 35, 569.

Thermolysis of N-(acyloxy)pyridine-2(1H)-thiones ‌10‌, derived from aliphatic carboxylic acids and N-hydroxypyridine-2(1H)-thione ‌9‌ (Y = H) in the presence of an iodine donor, undergo a radical chain reaction, which results in the overall loss of carbon dioxide and the formation of an iodoalkane ‌11‌ (‌Scheme 3‌).[‌6‌,‌7‌,‌34‌–‌37‌] The analogous thiohydroxamic ester, derived from 4-methylthiazole-2(3H)-thione is an equally suitable starting material for iododecarboxylation.[‌38‌] The N-(acyloxy)pyridine-2(1H)-thiones (“Barton esters”, ‌10‌) are obtained by reacting an acid chloride with the sodium salt of N-hydroxypyridine-2(1H)-thione (‌9‌, Y = Na) and a catalytic amount of 4-(dimethylamino)pyridine.[‌6‌,‌35‌,‌36‌,‌39‌–‌42‌] Alternatively, the free acid may be condensed with N-hydroxypyridine-2(1H)-thione (‌9‌, Y = H) and dicyclohexylcarbodiimide in dichloromethane.[‌34‌,‌36‌,‌43‌,‌44‌] The iododecarboxylation reaction is conveniently performed without isolation of intermediate ‌10‌. As well as triiodomethane[‌41‌,‌42‌,‌45‌,‌46‌] and molecular iodine[‌6‌] as the initial radical source, iodoacetonitrile[‌47‌] or 1,1,1-trifluoro-2-iodoethane[‌6‌,‌34‌–‌36‌,‌40‌,‌43‌,‌44‌] may also be used as efficient iodine atom donors. A slight excess of the iodine source, which in certain cases may also serve as the solvent, is required to compensate for radical chain side reactions. Visible-light-induced radical decomposition of ‌10‌ at ambient temperature in the presence of triiodomethane, represents a mild alternative to thermal treatment.[‌45‌] Ultrasonic irradiation of ‌10‌ in carbon tetrachloride also affords the iododecarboxylation product.[‌42‌]

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‌Meeeeeeeeee 8‌

M8	M	Meeeeeeeeee	Meeee (%) ee ‌88‌	Mee
(MM8)88Me	MM	MMM8, MMe8, eν, 88°M	88	[‌88‌]
(MM8)88Me	Me	MMM8, eeee, eeeeee	88	[‌8‌]
(MM8)88Me	Me	M8, eeeeeee, eeee, eeeeee	88	[‌8‌]
(MM8)88Me	Me	MMM8, MMe8, eeeeeeeeee (88 eMe, 88 M·ee−8), eeee, 88 eee	88	[‌88‌]
(MM8)88Me	MM	MMMM8M, eeeeeee, eν, 88°M, 8 eee	88	[‌88‌]
	Me	MM8MM8M, MM8Me8, eν, 88 eee	88	[‌88‌]
	Me	MMM8, eeeeeeeeeee, eeee, eeeeee, 88 e	88	[‌88‌]
MMMe8	Me	MMM8, eeeeee	88	[‌8‌]
	Me	MMM8, MMe8, eν, 88°M	88	[‌88‌]
	MM	MMM8, MMe8, eeeeeeeeee (88 eMe, 88 M·ee−8), eeee, 88 eee	88	[‌88‌]
	MM	MMM8, MMe8, eν, 88°M	88	[‌88‌]
	Me	MM8MM8M, eeeeeee, eν, 88 eee	88–88	[‌88‌,‌88‌]

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(8M,8M,8M)-8-(Meeeeeeeee)-8-eeeeee-8-(eeeeeeeeeeeeeeeeee)eeeeeeeeeeeeeee [‌88‌, M8 = (8M,8M,8M)-8-Meeeee-8-(eeeeeeeeeeeeeeeeee)eeeeeeeeeeeeeee-8-ee]; Meeeeee Meeeeeeee:[‌88‌]

Me e eeee ee (8M,8M,8M)-8-(eeeeeeeeee)-8-eeeeee-8-(eeeeeeeeeeeeeeeeee)eeeeeeeeeeeeeee-8-eeeeeeee eeee (88 ee, 8.88 eeee) ee eeeee eeeeeee (8 eM) (MMMMMMM: eeeeeeeeee) eee eeeee eeeeeeee (8 eeee) eee MMM (8 eeee). Mee eeee eee eeeeee ee 8°M eee eeeeee eeeeeeee (8.88 e, 8.88 eeee) eee eeeee ee eee eeeeeee eeee eeeeeeee. Meeee 8 e ee 8°M, eee eeeeeee eee eeeeeee ee eeeeeeeeeee, eee eeeeeee eee eeeee ee ee eeeee eeeeeee (8 eM), eee eee eeeeeee eee eeeeeee ee eeeeeeeeeee eeeee. Mee eeeeeee eee eeeeeeeee ee eeeee eeeeeeeeeee (88 eM) eeeeeeeeee MMM8 (888 ee, 8.88 eeee), eee Me eeee ee M-eeeeeeeeeeeeeee-8(8M)-eeeeee (‌8‌, M = Me; 88 ee, 8.88 eeee), eee MMMM (8 ee). Meeee 88 e ee eeeeee, eee eeeeeeeee eeeeeeeeee eee eeeeee ee ee eee eeeeeeee eeeeeee Meeeee. Meeeeeeeeeeee ee eee eeeeeeee eee eeeeeeeeeeeeeee eeeeeeeeeeee (eeeeee eee, MeMMe/eeeeeeeee eeeee 8:88) eeee e eeeeeeeee eee; eeeee: 88 ee (88%).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) M 88e8, 888.