Ester interchange, between ethyl

In analogous fashion, ester interchange between methyl benzilate and N-ethyl-N-n-propyl-ethanolamine yields benapryzine (63). 5... 

A somewhat different route is used to prepare an analogue that bears additional oxygen. The sequence, in this case, starts by base-catalyzed formylation of the hydro-cinnamic acid derivative (40-1) with ethyl formate. Condensation of the product (40-2) with guanidine in this case leads to a pyrimidone (40-3), with the cyclization involving an ester-amide interchange between guanidine and the ester. Reaction of... 

Such interchanges include the molecular rearrangement of completely esteri-fied esters of glycerol and mixtures of fatty acids, such as vegetable and animal oils—e.g., cottonseed oil or tallow the ester-ester exchange between aromatic carboxylic acid esters of a monohydric alcohol, such as o-CeH (C02CH3)2, and aliphatic carboxylic acid esters of a polyhydric alcohol, such as triacetin or between monohydric alcohol esters of aliphatic carboxylic acids—e.g., ethyl stearate —and fatty acid esters of polyhydric alcohol—e.g., tributyrin or triolein. 

The interchange reaction between a thioxoester and a thiol does not, in general, represent a meaningful synthetic procedure since dithioesters are more readily available than thioxoesters in most cases. However, 0,S-diethyl tiithiomalonate (61b) and diethyl tetrathiomalonate (61c) were prepared from 0,0-di-ethyl dithiomalonate (61a). On the other hand, the transformation of one dithiocarboxylic ester into another can be a useful and practicable reaction. For instance, ethyl arenecarbodithioates are intercon-verted to 2-dialkylaminoethyl arenecarbodithioates, according to equation (62). 

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