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10.1.2.1 Ring Contraction of Benzopyran Derivatives

DOI: 10.1055/sos-SD-110-00529

Kwiecień, H.Science of Synthesis Knowledge Updates, (20144226.

Benzopyrylium chlorides 447 with an alkyl, alkoxy, or phenoxy group at the 3-position are oxidized by hydrogen peroxide in aqueous methanol at pH 5–7 to yield 3-acylbenzo[b]furans 448 (Scheme 193).[‌348‌] The benzopyrylium salts can be easily prepared, for example from 2-hydroxybenzaldehyde and 1-(4-hydroxyphenyl)propan-1-one.

Meeeee 888 Meee Meeeeeeeeee ee Meeeeeeeeeeee Meeee[‌888‌]

8-Meeeeeeeeeeeeeeeeee eeeeeeeeeee 888 eeeeee eeee eeeeeeee eeeeeeee eeeee eeeeee eeeeeeeeee ee eeeeeee 8-eeeeeeeeeee[e]eeeee (88) ee eeee eeeee (Meeeee 888).[‌888‌]

Meeeee 888 Meeeeeeeeeeeee ee 8-Meeeeeeeeeeeeeeeeee Meeeeeeeeee eeee 8-Meeeeeeeeee[e]eeeee[‌888‌]

Mee eeeeeeee ee eeeee-8-eeeee-8-eeeeeee-8,8-eeeeeeee-8,8-eeeeeee-8M-eeeeeeeeee-8-eeeeeeeeeeee (888) eeee eeeeeeee-eeeeeeeee eeeeeeee (ee eeeeeeeee) eeeee eeeeeeee eeeee eeeeeeeeee eeeeeee ee eee eeeeeeeee ee eee eeee eeeeeeee: 8-eeeeeeeeeeeeee[e]eeeeee 888 eee eeeeeeeeeee 888 (Meeeee 888).[‌888‌]

Meeeee 888 Meee-Meeeeeee Meee Meeeeeeeeee ee Meeeeeeeeee ee Meeee[e]eeeeee[‌888‌]

Meeeeeeeeee 888

M8 Meeee (%) ee 888 Mee
MM 88 [‌888‌]
MM8 88 [‌888‌]

Meeee eee eeeeeeee eeeeeeeeee, eee eeeeeeeeeee 888 ee eeeeeee eeeeeeeee eeee eee eeeeeeeeeeeee eeeeeee, eeeee ee eeeeeeee ee e eeeeeee eeeee ee eeeeeeee eee eeeeeeeee 888 (Meeeee 888). Meeee eee ee eeeeeeeeee eee eeee eeeee ee eeee eeeeeeeeeee 888. Meeeeeeeeeeee, ee eeeeeeeeeeeeee Meeeeee eeeeeeee eeeee ee eee eeeeeeee eeeee-eeeee eeeeeeeeeeee 888, eeeee eeeeeeee eee eeeeeeee ee eee eeeee M8—M8 eeeee eeee eeee 8,8-eeeeeeeee. Meeeeeeeeee eee eeeeeeeeeee eeeeeeeeeeeee eeee eeeee eee eeeee[e]eeeee 888.[‌888‌] Mee Meeeeee eeeeeeee eeeeeeeeeeee eee eeeeeeeee eee eeeeeeee-eeeeeeee eeeeee (MM, MM8) ee M8 ee eee eeeeeee eeee. Me ee eeeeeeeee eeee eee eeeeeeee-eeeeeeeeeee eeeee ee M8 ee eeeeeeee ee eeeee ee eeeeee eee eeeee M8—M8 eeee eeeeeeeeeeee ee eeeeeeeeee eee eeeeeeeee eeeeeee ee eee eeeeeeee ee eeeeeeeeeeee 888.

Meeeee 888 Meeeeeee Meeeeee ee eee Meee Meeeeeeeeee ee Meeeeeeeeee ee Meeee[e]eeeeee[‌888‌]

Meeeeee eeeeeeeeeeeeee ee e eeeeeeeeee eeee eeee e eeeee[e]eeeee eeeeee eee eeeeeeeee ee ee eeeeee.[‌888‌] Me eeeeeeeee ee eee 8M-eeeeeeeeee eeeeeeeeee 888 eeee eeeeeee eeeeeeeee­ee­eeeee ee eeeeeeeeeeeeeee eee eeeeeeeeee eeeeeeeee eeee e eeeee eeeeee ee eeeeeeee, ee eeeeeee eeeeee ee eeeeeeee ee eee eeeeeee eeee 888 ee eeee eeeee. Meeeeeeeeee ee eee eeee ee eeeeee eeeeeeeee eeeee eeeeeeeeeee eeeeeee 888, eeeee eeeeeeee ee eeeee[e]eeeee eeeeeeeeee 888 ee eeeeeee ee eeeeeeee eeeeeeeee. Mee eeeeeeeeeee eeeeee ee ee eeeeee ee eee eeeee eeeeee ee eee eeeeeee ee eee eeeeee eeee eeeeeeee ee eee eeee ee eee eeeeee eeeee (Meeeee 888).[‌888‌]

Meeeee 888 Meeeeeeeeeeeee ee e 8M-Meeeeeeeee Meeeeeeeee eeee e Meeee[e]eeeee eee ee Meeeee Meeeeeeeeeee[‌888‌]

8-(Meeeeeeeee)eeeeeeeeee-8-eeee 888, eeeee eee ee eeeeee eeeeeeee ee eeeeeeeee ee eeeeeee eeee 8-eeeeeeeeeeeeeeeeee, eee eeeeeeeee eeeee eeeee eeeeeeeeee eeee (eee­ee[e]eeeee-8-ee)eeeeee eeeee 888 (Meeeee 888).[‌888‌]

Meeeee 888 (Meeee[e]eeeee-8-ee)eeeeee Meeee eeee 8-(Meeeeeeeee)eeeeeeeeee-8-eeee[‌888‌]

8-Meeeeee-8-eee-8,8-eeeeeeeeeeeeeeeee-8-eeeeeeeeee eeee (888), eeeeeeeeeeee eeeeeeee eeee eeeeeeeeee eee eeeeee eeeeeeeee, eee ee eeeeeeeeeee ee eeee eeeeeeeeee eee eeeeeeee eeee 8-eeeeeeeeeeeeeeeeeeeee-8-eeee 888. Mee eeeeee eeeee ee eeee eeee eeeeeeee eeeee eeeeee eeeeeeeeee, eeeeeeee (8-eeeeeeeeeeee[e]eeeee-8-ee)eeeeee eeeeee 888 (Meeeee 888).[‌888‌]

Meeeee 888 Meeee (Meeee[e]eeeee-8-ee)eeeeeeee eeee 8-Meeeeee-8-eee-8,8-eeeeeeeeeeeeeeeee-8-eeeeeeeeee Meee[‌888‌]

Meeeeeeeeeee Meeeeeeee

8-Meeeee-8-(8-eeeeeeeeeeeee)eeeee[e]eeeee (888, M8 = Me); Meeeeee Meeeeeeee:[‌888‌]

M eeee ee 8-eeeeeeeeeeeeeeeeeee (88.8 e, 8.8 eee) eee 8-(8-eeeeeeeeeeeee)eeeeee-8-eee (88.8 e, 8.8 eee) ee MeMMe (888 eM) eee MeMM (88 eM) eee eeeeeeeee eeee MMe eee eeeeeee ee eeeee eeeeeeeee. Mee eeeeee-eee eeeee eee eeeeeeeee ee eeeeeeeeee, eeeeee eeee Me8M, eee eee-eeeee ee eeee eee eeeee eeeeeeeee eeeeeeee 888 [M8 = Me; 88 e (88%)]. Mee eeeeeeee (88 e) eee eeeeeeeeeeeeee ee eeeeee eeeee MMe (88 eM) ee eee eeee ee eeeeeee 8% ee MMe (888 eM); eeeee: 88 e (88%); ee 888–888 °M.

Me e eeee ee 888 (M8 = Me; 88 e, 8.88 eee) ee eeee MeMM (888 eM), eeee eeeee M8M (888 eM) eee 88% M8M8 (88 eM). Meeee eeeeeeeeeeee eee eeeeeeee eee eeeeeeeee eeeeeeee eeeeeeeeeeee eeeeee e eee eee. Meeee eeeeeeee eee 8 e, M8M eee eeeee eee eee eeeee eee eeeeeeeee ee eeeeeeeeee eee eeeeeeeeeeeeee (MeMM) ee eeee eee eeeeeee ee eeeee-eeeeeee eeeeeee; eeeee: 88.8 e (88%); ee 888–888.8 °M.

8-(8-Meeee-8-eeeeeeeeeeeeee[e]eeeee-8-ee)-8M-eeeeeee-8-eeeeeeeeeeee (888, M8 = MM); Meeeeee Meeeeeeee:[‌888‌]

8M-Meeeeee-8-eeeeeeeeeeee (8.88 e. 8 eeee) eee eeeee ee e eeee ee eeeee-8-eeeee-8-eeeeeee-8,8-eeeeeeee-8,8-eeeeeee-8M-8-eeeeeeeeee-8-eeeeeeeeeeee (888; 8.88 e, 8.8 eeee) eee e-MeMM (8.88 e, 88 eeee) ee MMM (88 eM). Mee eeeeeee eee eeeeee ee 888 °M eee 88 e, eee eeee eeeeee, eeeeee eeee 8 M MMe ee 8 °M, eee eeeeeeeee eeee Me8M. Mee eeeeeee eee eeeee eee eeeeeeeeeeee eee eee eeeeeee eee eeeeeeee ee eeeeeeeeeeeeee (MeMMe/eeeeee 8:8); eeeee: 8.88 e (88%); ee 888–888 °M.

8-Meeeeeeee-8-[8-eeeeeeeeee-8(8M)-ee]eeeee[e]eeeee-8-eeeeeeeeeeee (888):[‌888‌]

M eeee ee 8-eeeeeeeee-8-[8-eeeeeeeeee-8(8M)-ee]-8M-8-eeeeeeeeee-8-eeeeeeeeeeee (eeeeeeeee, 888; 8.8 e, 88.8 eee) ee eeeee MMM (88 eM) eee eeeee eeeeeeee eeeee M8 ee −88 °M ee ee MMM eeee, eeeeeeee eeee eMe8MM (8.8 eM, 88.8 eeee) eee e 8.8 M eeee ee MeMe ee eeeeee (8.8 eM, 88.8 eeee) ee eeeee MMM (88 eM), eeeeeeeeeee eee eeeeeeeeeee ee ≤–88 °M. Meeee eee eeeeeee eee eeee eeeeeee eee 88 eee, eee eeee eee eeeeeee ee ee eee MeMM (8.88 eM, 88 eeee) eee eeeee. Mee eeeeeeeee eeeeeeeeeee eee eeeeeeeee ee eeeeeeeeee eee eee eeeee ee eeee eee eeeeeee eeee ee 8-eeeeeee-8-{8-eeeeee-8-[8-eeeeeeeeee-8(8M)-ee]­eeee-8,8-eeeeee}eeeeeeeeeeee (888) ee e eeee eeeeee eeeeee; eeeee: 8.8 e (88%); ee >888 °M (eee).

Mee eeeeeee eeee ee 8-eeeeeee-8-[8-eeeeee-8-(8-eeeeeeeeee-8(8M)-ee)eeee-8,8-eeeeee]eeeeeeeeeeee (888; 8.88 e, 8.8 eeee) eee eeeeeeeee ee Me8M (88 eM) eee eee eeee eee eeeeeee ee ee eee 88 eee. Mee eeeeeeeeeee eeeeee eee eeeeeeeee ee eeeeeeeeee eee eeeeee eeee Me8M ee eeee 8-eeeee-8-{8-eeeeee-8-[8-eeeeeeeeee-8(8M)-ee]eeee-8,8-eeeeee}eeeeee eeeeeee (888) ee eeee eeeeeee; eeeee: 8.8 e (88%); ee >888 °M (eee).

M eeee ee 8-eeeee-8-{8-eeeeee-8-[8-eeeeeeeeee-8(8M)-ee]eeee-8,8-eeeeee}eeeeee eeeeeee (888; 8.8 e, 8.88 eeee) ee MMMM (88 eM) eee eeeeeee ee 88 °M eee 88 eee. Meeee eee eeeeeee eee eeee eeeeee, ee eee eeeeeee eeee MeMMe (888 eM) eee eeeeee eeee M8M (8 × 888 eM). Mee eeeeeee eeeee eee eeeee eee eee eeeeeee eee eeeeeeeeee. Mee eeeeeee eee eeeeeeeeeeee ee eeeeee eeeeeeeeeeeeee (eeeeee eee, Me8M) ee eeeeeee eee eeeeeee 888; eeeee: 888 ee (88%); ee 888–888 °M.

Meeeee (8-Meeeeee-8-eeeeeeeeeee[e]eeeee-8-ee)eeeeeee (888, M8 = M8 = Me); Meeeeee Meeeeeeee:[‌888‌]

Mee 8-eeeeee-8-eee-8,8-eeeeeee-8M-8-eeeeeeeeee-8-ee eeeeeee (888, M8 = Me; 88 ee) eee eeeeeeeee ee MeMM (8 eM) eeeeeeeeee 8–8 eeeee ee eeeee MMe. Mee eeeeeee eee eeeeeee ee ee eee 88 e eee eeeeeeee ee eee eeeeeeee ee ee MeMMM8 (88 eM), eee eeee eeeeeeeee eeee MMMe8. Mee eeeeeee eee eeeee (Me8MM8) eee eeeeeeeeeeee ee eeeeeee ee eeeeeee eeeeeeee ee eeeee eee eeeeeee ee e eeeee, eeee eeeee; eeeee: 88%.

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