�ber Carbons�ureester der Phloroglucine

Boron, Trichloride as a Selective Demethylating Agent for Hindered Ethers: a Synthesis of the Phytoalexins α- and Β-Pyrufuran, a Synthesis of Tri-O-methylleprolomin and its Demethylation

“…This ester (4.6 g) and bromine (2.4 g) were stirred and heated under reflux in carbon tetrachloride (50 ml) for 0.5 h, and the solution was then set aside for 12 h. The usual workup gave methyl I-acetoxy-7-bvomo-5,8-dimethoxynaphthalene-2carboxylate (5.7 6(CC14, 60 MHz) 2.53, s, 3, Me; 3.74, s, 3, OMe; 3.97, s, 6 , 2 x OMe; 4.05, s, 3, OMe; 7.34 and 8.28, AB, J 2 H z , 2, H3,l. (42) The bromo ester (37) The Grignard reagent was made in the usual way from 3,5-dimethoxybenzyl bromide (38.1 g),25 anhydrous ether (250 ml) and magnesium (2.1 g). The solution was cooled to 0" and anhydrous iron(111) chloride (0.7 g) was added, and the solution was then stirred and heated under reflux for 1 h. The cooled solution was poured on ice and dilute hydrochloric acid.…”

“…Workup with ether after 26 h gave the crude product which was distilled under diminished pressure and afforded 2-methoxy-6-methylphenol(14) (1 .64 g, 90 %), which formed transparent prisms (from cold light petroleum), m.p. [41][42].…”

“…with 20 % ethyl acetate/light petroleum as developer. A band of higher RF yielded methyl 4-acetoxy-5,7-dimethoxynaphthalene-2-carboxylate (20.5 mg, 11 (42) In a similar manner to that described for compound (35), the substrate (42) (871 mg, 30.0 rnmol) in dichlorornethane (20 ml) was treated with boron trichloride (1.764 g, 150 mmol) in dichloromethane (2.9 ml) during 3.5 h. The crude product was acetylated and the acetate was crystallized from methanol as plates (935 mg, 90%) of methyl 4,5-diacetoxy-8-methoxy-6-methylnaphthalene-2-carboxylate, 62.1 ;H,5.4. Cl8Hl8O7 requires C,62.4;H,5.2%).…”