P-Methoxyphenyllead triacetate

The chloroform solution Is washed with water (2 x 250 ml) and stirred with glacial acetic acid (250 ml) for 1 hr (Note 6). The solution that results Is washed with water (2 x 250 mL), and the chloroform phase is treated with 1.5 L of hexane and kept at 2 C for 48 hr. The material which precipitates Is collected and dried at 0.1 ram In a desiccator (calcium chloride) for 5 hr to give p-methoxyphenyllead triacetate (20-22 g, 35-40%) as pale yellow crystals, mp 138-139°C (Note 7). The product may be kept for at least 3 weeks If stored at 2°C In a sealed container. 

The procedure described here serves to illustrate a new, general method for effecting the < -arylation of g-dicarbonyl compounds by means of an aryllead triacetate under very mild conditions. Although the first synthesis of an aryllead triacetate was reported relatively recently, a wide range of these compounds can now be readily prepared. The most direct route to these compounds is plumbation of an aromatic compound with lead tetraacetate, and in the procedure reported here p-methoxyphenyllead triacetate has been prepared in this way. It may also be obtained by reaction of the diarylmercury with lead tetraacetate, a longer, but more general method of synthesis of aryllead triacetates. 

The first synthesis of p-methoxyphenyllead triacetate by direct plumbation was reported by Harvey and Morman, who obtained the compound in 2418 yield by heating anisole and lead tetraacetate in acetic acid at SO C for 4... 

A. p-Methoxyphenyllead triacetate. A 1-L Erlenmeyer flask, equipped with a magnetic stirring bar, is charged with 50 g (0.11 mol) of lead tetraacetate (Mote 1), chloroform (200 mL), and 140 g (1.09 mol) of dichloroacetic acid (Note 2). To this solution is added 16 g (0.15 mol) of anisole (Note 3), and the mixture is stirred at 25°C until lead tetraacetate can no longer be detected (Note 4). The reaction mixture is washed with water (2 x 250 mL) and the chloroform solution is treated with 1.5 L of hexane (Note 5). The yellow... 

The treatment of 1 - TV-morpholinocyclopentene with p-methoxyphenyllead triacetate in chloroform at room temperature provides a simple high-yielding route to 2-p-... 

A mixture of mesitol, p-methoxyphenyllead triacetate, and pyridine in equimolar quantities in chloroform gives an almost quantitative yield of fhe 6-arylcyclohexa-2,4-dienone and the 4-arylcyclohexa-2,5-dienone in a ratio of 4 1 (Scheme 13.19) [45], There is a marked preference for ortho arylation. 

METH0XYCYCL0HEXAN-1-0NE-3b,4b-DICARB0XYLIC ACID ANHYDRIDE, 61, 147 p-Methoxyphenyllead, 62, 30 p-Methoxyphenyllead triacetate, 62. 24... 

The silyl enol ethers of ketones react with aryllead triacetates to afford completely different types of product, depending on the nature of the substrate. The reaction of cyclohexanone trimethylsilyl enol ether with 4-methoxyphenyllead triacetate (15) afforded a mixture of 2-p-anisylcyclohexanone (44%) and 2-acetoxycyclohexanone (32%). ... 

Similarly to P-diketones a number of other p-oxo esters can also be readily arylated with a variety of aryllead triacetates. This was first reported by Pinhey in the arylation of ethyl 2-oxocyclopentanecarboxylate (153) with 4-methoxyphenyllead triacetate (141) in chloroform and pyridine in high yields (Scheme 4.41). The ideal conditions reported the use of 3.0 equivalents of pyridine to 1.0 equivalent of a-ryllead triacetate [89]. Moreover this approach could be utilised to generate a-aryl ketones following decarboxylation of the P-ketoester. Other examples include the a-arylation of 3- and 4-hydroxycoumarins [90, 91]. 

The title compound was prepared according to the general procedure using p-keto allyl ester (3) (250 mg, 1.49 mmol) and 4-methoxyphenyllead triacetate (879 mg, 1.79 mmol) to yield the product as a colourless oil (247 mg, 61 %). 

---