Para-anisoyl chloride

In another approach the same starting C-glycoside 239 was acylated with para-anisoyl chloride to form the ester 242, which was treated with lithium diisopropylamide (LDA) to give the enol of a dibenzoylmethane 243 (equation 110) ° . 

The dealuminated Y(30) zeolite efficiently promotes the benzoyla-tion of 2-butylbenzofuran with para-anisoyl chloride or para-anisic acid the reaction is performed at 180°C in 1,2-dichlorobenzene (Table 4.6), and leads to the three acylated isomers 15,16, and 17 with a good initial selectivity in the 3-acylated derivative 15. The selectivity decreases with time due to the consecutive deacylation of this compound, followed by a reacylation that favors the formation of the other two isomers (mainly, the 6-acylated one). As expected, lower activity is observed when the carboxylic acid is utilized as acylating agent. 

A variant on this theme contains mixed acyl groups. In the absence of a specific reference it may be speculated that the synthesis starts with the diacetyl derivative (15). Controlled hydrolysis would probably give the monoacetate (16) since the ester para to the ketone should be activated by that carbonyl function. Acylation with anisoyl chloride followed by reduction would then afford nisobuterol (18). 

There are a number of synthetic routes available to access the benzhy-drols needed for this approach. The first published route to SNC80 used a Friedel-Crafts acylation of toluene with m-anisoyl chloride to yield a benzo-phenone, followed by sodium borohydride reduction of the ketone (after the three-step elaboration of the para-methyl group into the diethylcarboxamide, Scheme 3) [23,24],... 

Table 4.6 Comparison of selectivity in the benzoylation of 2-butylbenzofuran with parfl-anisoyl chloride or para-anisic acid in the presence of Y zeolite...

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See also in sourсe #XX -- [ ]

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