Science of Synthesis

Takeda, T.; Tsubouchi, A., Science of Synthesis, (2007) 30, 120.

Acyclic dithioacetals ‌1‌ are prepared by condensation of aldehydes or ketones with 2 equivalents of thiols in the presence of protic acids such as hydrogen chloride,[‌1‌–‌6‌] sulfuric acid,[‌7‌] or 4-toluenesulfonic acid[‌8‌,‌9‌] (‌Table 1‌). These catalysts are suitable for the large-scale preparation of dithioacetals since the catalysts are inexpensive and are readily available. The thioacetalization of carbohydrates is also carried out in the presence of these protic acids.[‌10‌,‌11‌] However, this method has a drawback in that it cannot be applied to substrates possessing acid-labile groups. An improved procedure, in which a catalytic amount of hydrogen chloride is generated in situ by the reaction of acetyl chloride with methanol, overcomes such a disadvantage, allowing the thioacetalization of acid-sensitive substrates.[‌12‌]

‌Meeee 8‌ Meeeeeeee ee Meeeeeeeeeeee ee Meeeee Meee Meeeeeeee Meeeeeeeeeeeeeeee[‌8‌,‌8‌,‌8‌,‌8‌]

e Meeeeeeee = 8,8-eeeeeeeeeee-8-eeeeeeeeee.

Meeeeeeeeeee Meeeeeeee

Meeeeee Meeeeeeeeeeee ‌8‌ (M8 = Me); Meeeeee Meeeeeeee:[‌8‌]

Me eeeeeeee ee eeeeee (8 eeeee) eee eeeee eeee MeMM (8 eeeee). Mee eeeeeee eee eeeeee ee 88–88°M eee eeeeeee eeeee eeeee e eeee eeee ee eee MMe eee eeeeee eeee eee eeee. Meeee eeeeeeee ee M8M, eee eeeeeee eee eeeee eeeeeeeee ee eeeeee eeeeeeee eeeeeeeee. Mee eeeeeeee eee eee eeeeeeeee eee eeeee (MeMe8). Meeeeeeeee eeeeeeeeeeee eeeee eeeeeee eeeeeeee eeee eee eeeeeeeeeeeee; eeeee: 88–88%.

8,8-Mee(eeeeeeeeeeeeee)eeeeee (‌8‌, M8 = M; M8 = Me; M8 = Me); Meeeeee Meeeeeeee:[‌8‌]

MMe eee eeeeeee eeeeeee e eeeeeee eee-eeeeee eeee ee eeeeeee (8.8 e, 88 eeee) ee MeMM (88 eM, 888 eeee) eee 8 e. Mee eeeeeee eee eeeeeee eee e eeeeeee 8 e ee ee eeeeee ee ee. Me8M (888 eM) eee eeee eeeee eee eee eeee eee eeeeee eeee 88% MeMM (8 × 88 eM) eee M8M (8 × 88 eM), eeeee (MeMM8), eee eeeeeeeeee eeeee eeeeeee eeeeeeee ee eeee ee eee. Meeeeeeeeeee eeee eee eeeeeee; eeeee: 88.88 e (88%); ee 888–888°M/8.8 Meee.

Meeeeeee Meeeeeeeeeeee ‌8‌ (M8 = M; M8 = Me); Meeeeee Meeeeeeee:[‌8‌]

M eeeeeeeee eeeeee (8 ee%) ee eeeee MMe eee MeMM (8.8 eeeee) eeee eeeeeeeeeeee eeeee ee e eeeeeee eeeeeeeee eeeeeeee ee −88°M. M eeeee eeeeeeee ee eeeeeeeeeee eee eeeeeeee. Mee eeeee eeeeeee (eee eeeeee) eee eeeeeeeeeee eeee eee. ee Me8MM8 eee eeeeeeeee (Me8M). Mee eeeeeeee eeeeeee eeeeee eeee eeeee (Me8MM8) eee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeeeeeeeee; eeeee: 88–88%.

Meeeeeee Meeeeeeeeeeee ‌8‌ [M8 = M; M8 = MM8M8 (M = M, 8-Me, 8-Me, 8-MM), Meeeeeeee, MMe8; M8 = MM8M8MM8 (M = M, 8-Me, 8-Me, 8-Me, 8-Me, 8-Me)]; Meeeeee Meeeeeeee:[‌8‌]

M eeeeeee ee ee eeeeeeee (8 eee) eee ee eeeeeeeeeee eeeee (8 eee) eee eeeee ee eee-eeeeee (eeeee 8°M) M8MM8 (888 eM), eeee eeeeeeee eeeeeeee. Meeee eee eeeeeeee eee eeeeeeee, eee eeeeeee eee eeee ee ee eee eeee eee ee eeeeeeeeee 8 e eee eeeeee eeee eeeeeee eee. Mee eeeeeeeeeeee eeeeeee eee eeeeeeeee ee eeeeeee eeeeeeeeee eee eeeeee eeee eee eeeee eeeeeee eeeee eeeee ee eee eeee ee eeee. Mee eeeee eeeeeee eee eeeeeeeeeeeeee [eeeeeee (MMMMMMM: eeeeeeeeee) ee eeeeeeeee eeeee]; eeeee: 88–88%.

8,8-Meeeeee-8,8-eeeeeeeeeee-8-eeeeeeeeeeee Meeeeeee Meeeeeeeeeee {‌8‌, M8 = M; M8 = 8,8-Meeeeee-8,8-eeeeeeeeeee-8-ee; M8 = Me; 8-[Mee(eeeeeeeeeeeeee)eeeeee]-8,8-eeeeeee-8,8-eeeeeeeeeee}:[‌8‌]

M eeee ee 8,8-eeeeeee-8,8-eeeeeeeeeee-8-eeeeeeeeeeee (8.8 e, 8.88 eeee), MeMM (8.8 eM, 88.8 eeee), eee e eeeeeeeee eeeeee ee MeMM ee eee eeeeeee (88 eM) eee eeeeeee ee 888°M eee 8 e. Mee eeeeee eeeeeee eee eeee eeeeeeeee eeee Me8M (8 × 88 eM), eeeee, eee eeeeeeee. Mee eeeeeee eee eeeeeee eeeee eeeeeee eeeeeeee ee eeeee eee eeeeeee ee ee eee; eeeee: 8.8 e (88%).

References

Meeeeee Meeeeeeeeee

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