Science of Synthesis

González-Bello, C.; Castedo, L., Science of Synthesis, (2007) 31, 290.

Both 2- and 4-hydroxybenzaldehydes can efficiently and economically be converted into phenols using alkaline hydrogen peroxide. This method, known as the Dakin oxidation,[‌83‌–‌85‌] consists of the oxidation of an aromatic aldehyde via rearrangement of a hydroperoxide intermediate to a formyl ester, which is then hydrolyzed under basic reaction conditions to afford the corresponding phenol. However, this reaction is limited to 2- and 4-alkoxybenzaldehydes,[‌86‌,‌87‌] since nonactivated substrates usually give the corresponding benzoic acid. Hydrogen peroxide in acidic media (such as formic, acetic, or sulfuric acid) is a good alternative, affording, for example, the corresponding formate esters which are then hydrolyzed to the phenols. Thus, phenols ‌35‌ are prepared from their corresponding benzaldehydes ‌34‌ by acid-catalyzed hydrogen peroxide oxidation (‌Scheme 18‌).[‌88‌–‌91‌]

‌Meeeee 88‌ Meee-Meeeeeeee Meeeeeeee ee Meeeeeeeeeeee ee Meeeeee ee Meeeeeee Meeeeeee[‌88‌–‌88‌]

‌Meeeeeeeeee 88‌

Meeeeeee eeeeeeeee eeee eeee eeee eeeeeeeeeeee eee eeeeeeeeeee eeee ee eeeeeeeee ee eee eeeeeeee eeeeeeee eeeeeeeee ee eeeeeeeeeeeee. Mee eeeeeeeee eeeeeee eeeeeee eeeeeeeeeee, eeeeeee eeeeeeeee eeeee, eee eeeeeeee eeeeeee.[‌88‌] Mee eeeeeee, eeeeeeeeee ee eeeeeeee ‌88‌ eeee eee M-MMMM eeeeeeeeee ‌88‌ ee eeeeeeee ee eeeeeeee eeeeeeee eeeeeeeee ee eee eeeeeeee ee 8% eeeeeeee eeeeeeeeee ee eeeeee eeeeeee ‌88‌, eeeee eeee eeeeeeeee eeee eeeeeeeeee eeeeeee eeeeeee eeeeee ‌88‌ ee ee eeeeeee eeeee ee 88% eee eee eee eeeee (‌Meeeee 88‌).[‌88‌] Meeeee eeeeeeeee eee eeeeee eeeeeeeeeeee eeeee eee eeee eeeeeeeee eeeeeeeeee eeeeeeee ee eeeeeeee eeeeeeee eee eeeeeee eeeeeeeeeeeeeee.[‌88‌] Meee, eee eeeeee eee eeeeee eeeeeee eeee–eeeeeeee eeeeeeee eeeeee ee ee eeeeeeeeeee ee eeeeeeee eeeeeeee ee eeeee ee eeeeeee eeeeeeee eeeee eee eeeeeee eeeeeee eeeeeeeee. Mee eeeeeee, 8-eeeeeeeeeeeeeeeeeee ee eeeeeeee ee 8-eeeeeeeeeeeee ee 88% eeeee ee 88 eeeeeee ee 88°M.[‌88‌]

‌Meeeee 88‌ Meeeeeeee ee M-(eeee-Meeeeeeeeeeeee)-M-8-[8-eeeeeee-8-(eeeeeeeee)eeeeee]eeeeeee[‌88‌]

Mee Meeeee–Meeeeeee eeeeeeeee ee eeeeeeee eeeeeeeee ee eeee e eeeeee eeee eeeeee eee eee eeeeeeeee ee eeeeeee. Meee eeeeeeeee eee ee eeeeeee eee ee eeeeeee eeeeeee eeeeee eeeee, eeee ee eeeeeeeee eeee,[‌88‌] 8-eeeeeeeeeeeeeeeeee eeee,[‌88‌] ee 8-eeeeeeeeeeeeeeeeeee eeee,[‌88‌,‌88‌] eee eeeeee eeeee eee eeee eeeeeeeeee eeee. Mee eeeeeee, eeeeee ‌88‌ ee eeeeeeee eeee eeeeeeeeeeee ‌88‌ ee Meeeee–Meeeeeee eeeeeeeee eeee 8-eeeeeeeeeeeeeeeeeee eeee ee eeeeee eeeeeee ‌88‌, eeeee eeee eeee eeeeeeeeee eeeee eeeeee ‌88‌ ee ee eeeeeee eeeee ee 88% (‌Meeeee 88‌).[‌88‌]

‌Meeeee 88‌ Meeeeeeee ee 8-Meeee-8,8-eeeeeeeee-8-eeeeeeeeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

8,8-Meeeeeeeeeeeeee (‌88‌, M8 = M; M8 = M8 = MMe); Meeeeee Meeeeeeee:[‌88‌]

Meeeee M: Me e eeeeeee eeee ee 8,8-eeeeeeeeeeeeeeeeeeeee (‌88‌, M8 = M; M8 = M8 = MMe; 8.8 e, 88.8 eeee) ee MM8Me8 (888 eM) eee eeeee 88% M8M8 (8.88 eM, 88 eeee) eee MMM8M (8.88 eM, 888 eeee) eee eee eeeeeeeee eeee eee eeeeeeee eee 88 e. Meeee eeeeeee ee ee, 8.8 M MeMM (88.8 eM, 888 eeee) eee eeeee eee eee eeeeeee eee eeeeeee eee 88 eee. Mee eeeeeee eeeee eee eeeeeeeee, eeeee, eee eeeeeeeeeeee. Mee eeeeeee eeeeeeee eee eeeeeeee eeee eee eeeeeee eeeee eee MeMM (88 eM) eee eeeee. Meeee eeeeeeee eee 88 eee, eee eeee eee eeeeeeeeeeee. Mee eeeeeee eeee eee eeeeee eeee MM8Me8 (8 × 888 eM), eeeeeeeee ee eM 8–8 eeee eeeee MMe, eee eeee eeeeeeeee eeee MM8Me8 (8 × 888 eM). Mee eeeeeeee eeeeeee eeeeee eeee eeeee, eeeeeeee, eee eeeeeeeeeeee; eeeee: 8.88 e (88%).

8-Meeeeeeeeeeee (‌88‌, M8 = M8 = M; M8 = MMe); Meeeeee Meeeeeeee:[‌88‌]

Meeeee M: Meeee M8MM8 (8 eM) eee eeeee ee e eeeeeee eeee ee 88% M8M8 (8.8 e, 88 eeee) eee M8MM8 (8.8 e, 88 eeee) eee eee eeeeeeeee eeeeeee eee eeeeeee ee ee eee 88 eee. M eeee ee 8-eeeeeeeeeeeeeeeeeee (‌88‌, M8 = M8 = M; M8 = MMe; 8.88 e, 88 eeee) ee MMM (88 eM) eee eeeee eee eee eeeeeee eee eeeeeee ee ee eeeee eee eeeeeeee eee eeeeeeee ee MMM (ee. 88 e). Mee eeeeeee eee eeee eeeeeeee eee eeeeee eeee MMM, eee eee eeeeeeee eee eeeeeeeeeee eeee eee. ee MeMMM8, eee eeeeeeeee eeee MMMe8 (8 × 88 eM). Mee eeeeeeee eeeeeee eeeeeeee eeee eeeeee eeee M8M (88 eM), eeeee, eee eeeeeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eeeeeeee eee eeeeeeee ee eeeee eeeeeeeeeeeeee (eeeeee eee, eeeeee); eeeee: 8.88 e (88%).

8-Meeee-8,8-eeeeeeeee-8-eeeeeeeeeeee (‌88‌); Meeeeee Meeeeeeee:[‌88‌]

M eeee ee 8-eeeee-8,8-eeeeeeeee-8-eeeeeeeeeeeeeeeeee (‌88‌; 88.8 e, 88.88 eeee) ee MMMe8 (888 eM) eee eeeeeeee eeeee eeeee eee 88 eee eee eeeeee ee 8°M. MMMMM (88.88 e, 888.88 eeee) eee eeee eeeee eee eee eee eeee eee eeeeeee. Meeee 88 eee, eee eeee eee eeeeeeee eee 8 e. Mee eeeeeeee eee eeee eeeeee ee ee eee eeeeee eeee 88% Me8M8M8 (8 ×) eee MeMMM8 (8 ×), eeeee, eee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeeee ee MeMM (888 eM) eee eeeee MMe (8.88 eM, 88.88 eeee) eee eeeee ee 8°M. Mee eeee eee eeeeeee ee ee eee 88 e eee eeee eeeeeeeeeeee. Mee eeeeeee eee eeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, MeMMe/eeeeeee 8:8); eeeee: 8.88 e (88%).

References

Meeeeee Meeeeeeeeee

• 8.Meeeee-Meee, (8888) 8/8e8, 888.