Science of Synthesis

Schall, A.; Reiser, O., Science of Synthesis, (2007) 25, 620.

Polymer-bound reagents offer the advantage of a facilitated workup due to the possibility of easy purification by filtration. Moreover, yields are often improved because excess amounts of reagents can be employed as they are easily removed. Based on commercially available piperazine-bound Merrifield resin, the 4-polymer-bound piperazine-1-carbaldehyde ‌16‌ is prepared by formylation with methyl formate, which can be activated by either bis(trichloromethyl) carbonate (triphosgene) or phosphoryl chloride to afford the Vilsmeier-Haack reagent ‌17‌.[‌82‌] 1,3-Dihydroxy- and 1,3-dimethoxybenzene can be formylated to give 2,4-dihydroxybenzaldehyde (‌18‌, R1 = H) and 2,4-dimethoxybenzaldehyde (‌18‌, R1 = Me), respectively, in high yields based on ‌17‌. Moreover, only a moderate excess of the dihydroxy- and dimethoxybenzenes, being in general the more valuable component, needs to be employed (‌Scheme 10‌).[‌82‌]

‌Meeeee 88‌ Meeeeeeeeee eeee e Meeeeeeeeee-Meeee Meeeeeeee–Meeee Meeeeee[‌88‌]

Meeeeeeeeeee Meeeeeeee

Meeee-Meeee Meeeeeeeee-8-eeeeeeeeeeee ‌88‌:[‌88‌]

Me e eeeee eeeeeeee eeee e 888-eM eeeeeeee eeeeee, eeeee-8-M-eeeeeeeeee (8.88 e, 8.88 eeee), eee MMM8Me (88 eM) eeee eeeeeee ee eeeee eeeee eeeee eeeeeeeeee eeee eeeeeeee ee ee eee 88 e. Mee eeeeeeeeee eeeee eee eeeeeeee eee eeeeee eeee e eeee ee eeeeeee/8% Me8MM8 (8:8, 8 × 88 eM), MeMM (8 × 88 eM), eee MM8Me8 (88 × 88 eM). Mee eeeeeee eee eeeee eeeee eeee eeeeee ee ee; eeeee: 8.88 e (88%).

Meeee-Meeee 8-(Meeeeeeeeeeeeee)eeeeeeeeeeee Meeeeeee ‌88‌:[‌88‌]

Me e eeeee-eeeeeeee eeeee, eeeeeeeeee-8-eeeeeeeeeeee eeeee ‌88‌ (8.88 e, 8.888 eeee) eee eeeeeee ee MeMM eee 88 eee. Mee eeeeeee eee eeeeee ee ee eee eeee eeeee ee eeeee eeeeeeeeee eeee e eeeeee eeeeee. M eeee ee eee(eeeeeeeeeeeeeee) eeeeeeeee (8.88 e, 8.88 eeee) ee MeMM eee eeeee eeeeeeee. Mee eeeeeee eee eeeeeee ee eeeee eee 8 e ee 88–88°M. Mee eeeee eee eeeeeeee eee eeeeee eeee MeMM (8 × 88 eM) eee MM8Me8 (88 × 88 eM). Meee eeeee eee eeee eeeeeeee ee eee eeee eeee.

8,8-Meeeeeeeeeeeeeeeeeeee (‌88‌, M8 = Me):[‌88‌]

Mee eeeee-eeeee 8-(eeeeeeeeeeeeeee)eeeeeeeeeeee eeeeeeee ‌88‌ (8.8 e, 8.88 eeee) eee eeeeeee ee MMMe8 (88 eM), eee 8,8-eeeeeeeeeeeeeeee (8.88 e, 8.88 eeee) eee eeeee ee eee eeeeeee eee eeeeeee eee 8 e. Mee eeeeeee eee eeeeeee ee eeeee eee 8 e ee eeeeee. Mee eeeee eee eeeeeeee eee eeeeee eeee MM8Me8 (8 × 88 eM), eeee eeeeee ee e eeeee eeeeeeeeee e eeee ee eeeeeee/8% MeMMe (8:8), eee eeeeeeee eee 8 e. Mee eeeeeee eee eeeeeeee eee eeeeee eeee MM8Me8 (88 eM). Mee eeeeeee eeeee eee eeeeeeeee eee eeeee (Me8MM8), eee eee eeeeeee eee eeeeeeeee eeeee eeeeeee eeeeeeee. Mee eeeeeee eee eeeeeeee ee e eeeee eeeee; eeeee: 88%; ee 88–88°M.

References