Ortho esters amidine synthesis

PINNER Imlno Ether Synthesis Synthesis of imlno ethers, amidines and ortho esters from nitnles. 

Since the discovery of the synthesis of 1,3,5-triazine-2,4-diamines from biguanide and its derivatives,328-329 a large variety of carboxylic acid derivatives, e.g. acid chlorides,332 342,346 lactones,333 amides,334,335 imides,336,337 ortho esters,338 amidines,338 esters334, 339- 343 and acid anhydrides,332,344,345 have been used as starting materials in the preparation of these triazines (Table 8).330,331 The preferred procedure is the reaction of biguanides 1 with esters 2 in alcoholic solution, sometimes in the presence of a basic catalyst. The reaction mechanism is thought to be as indicated.341... 

For most purposes, this amidine synthesis is preferable to the formamide and the ortho ester alternatives it occurs at a lower temperature than the former, and it is free from the intrusion of intermediates characteristic of the latter. It is particularly useful when an alkyl or chloroalkyl group is required in the 2-position of the product, this pathway being much less explored in the formamide and the ortho ester methods. The amidine reaction is suitable for both 7t-deficient and 7t-excessive nuclei. 

Pinner Reaction (Amidine and Ortho Ester Synthesis)... 

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