At last... Glad someone liked my post!
Anyway, would activating zinc for this synthesis be as simple as Barium's method of 'stirring in 20ml 5% aq. HCl for two minutes then washed with 3x50ml water and finally 20ml MeOH', scaled to size of course? And would a finer grade of zinc powder be beneficial, or would any decent purity zinc powder suffice?
Also, although it's related to Grignard-type organozinc reactions, a quote from https://www.thevespiary.org/rhodium/Rhodium/chemistry/grignard.notes.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/grignard.notes.html)
:
the undesireableity of using ether as a solvent in acid chloride reactions (because of ether cleavage and ester formation)
Is there anything to worry about here? Although anisole is acylated without ether cleavage, the methylene ether of benzodioxole is very sensitive to demethyleneation :( . Anisole can be acylated with AlCl3 as catalyst, whereas benzodioxole can't.
Zinc Mediated Friedel–Crafts Acylation in Solvent-Free Conditions under Microwave Irradiation
Satya Paul, Puja Nanda, Rajive Gupta, André Loupyb
Synthesis 2003(18), 2877–2881
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_imgs/pdf.gif)
Abstract
Zn powder is found to catalyze the Friedel–Crafts acylation of aromatic compounds with acyl halides efficiently under microwave irradiation in solvent-free conditions. Activated substrates undergo acylation predominantly at the para-position. The Zn powder can be re-used up to six times after simple washing with diethyl ether and dilute HCl.
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000408642-acylation.jpg)
Preparation of Acetophenone, Entry 1; Typical Procedure
To a mixture of benzene (0.078 g, 1 mmol) and Zn powder (0.065 g, 1 mmol) in a 50 mL borosil beaker, AcCl (0.078 g, 1 mmol) was added. The reaction mixture was mixed properly with the help of a glass rod (10 s) and then irradiated in a microwave oven for 30 s at 300 W (monitored by TLC). The reaction mixture was cooled and extracted with Et2O (3 × 10 mL). After drying the ether extracts over anhydrous Na2SO4, the acetophenone was obtained by removal of the solvent under reduced pressure. Finally, the product was purified by column chromatography (silica gel) using P.E. as eluent (0.114 g, 95%).
The reaction was also performed with benzene (0.390 g, 5 mmol), Zn powder (0.325 g, 5 mmol) and AcCl (0.390 g, 5 mmol) in a 50 mL borosil beaker following the same procedure. After an irradiation time of 30 s, acetophenone (0.56 g, 94%) was obtained by passing through column of silica gel and elution with P.E.
The structure of the products was confirmed by 1H NMR, IR and comparison with authentic samples obtained commercially or prepared by reported methods.