Orthoamides. LII. Contributions to the synthesis of carboxylic ortho acid amides

The formamidinium salts 11a, c as well as the nitrile 12 react with sodiumh ydride/dimethylamine in the presence of trimethylborate to give the ortho f ormic acid amide 3a. The orthoamides 6a and 16 can be prepared from the imi nium salts 15 and 14, resp, by the same procedure. Treatment of the azaviny logous formamidinium salt 15 with sodiumhydride and piperidine or morpholin e in the presence of trime-thylborate affords the orthoamides 6c and 6d, re sp. By transamination of the azavinylogous aminalester 5a are accessible th e orthoamides 6b-d. The vinylogous orthocarbonic acid derivative 17 can be obtained from the salt 14 and sodium alcoholates. The action of sodiumhydri de, dimethylamine and trimethylborate on the iminium salt 18 produces a mix ture of the orthocarbonic acid derivatives 7a, 8a, 9a. When the guanidinium salt 20 is treated with the same reagents the ortho-amides 3a and 10a are obtained. The reduction of the salt 20 with sodiumhydride in the presence o f several activating reagents (e.g. tetrabutyl orthotitanate, aluminiumisop ropylate, trimethylborate) affords the orthoamide 3a. The reduction of the iminium salts 18 and 24 does not proceed clean, giving mixtures of various orthoformic acid derivatives. The form-amidine 25 can be prepared by reduct ion of the salt 15 with sodiumhydride/trimethylborate with good yields. By the action of the corresponding carbanions on the guanidinium salt 20 can b e obtained the carboxylic acid orthoamides 26-33. By the same procedure the orthoamides of alkyne carboxylic acids 36a-h, j-n are accessible.