ORTHOAMIDES .50. CONTRIBUTION TO THE CHEM ISTRY OF PROPIOLALDEHYDAMINALES - SYNTHESIS AND TRANSFORMATIONS TO PUSH-PULL-SUBSTITUTED BUTA-1,3-DIENES, CYCLOBUTANES, VINYLOGOUS AMIDINIUM SALTS AND 1,2,3-TRIAZOLES

Tert-butylaminalester 5 reacts with terminal alkynes to give aminals o f substituted propiolaldehydes 3c,d. The aminal 3a is accessible from N,N,N,N'-tetramethylformamidinium chloride (7b) and sodium acetylide. The aminals 3b,c can also be prepared from bis(dimethylamino)acetonitr ile 8 and terminal alkynes in the presence of sodium hydride. The nitr ile 8 is also useful for the preparation of the bis-aminal of acetylen edialdehyde 6. The aminal 3e can be transaminated by heating with seco ndary amines to give the aminals 3f-i. The aminals 3a-i react with str ong CH2-acidic compounds (pK(a) between 9 and 14) to give the 1-dialky lamino-1,3-butadienes 10. The isomeric 1-dialkylamino-butadienes 18 ca n be obtained from the condensation of the CH-acidic cinnamic acid der ivatives 19 with dimethylformamidedimethylacetal. CH and NH-acidic com pounds as cyanacetamide react with the aminals 3c,e exclusively with t he acidic methylene group to produce the enamines 10h,t. The acylforma midine 21 can be obtained from 10t and tert-butylaminalester 5. The py ridone 22 is accessible from the condensation product 10h by thermal c yclization. The pyrido[2,3-d]pyrimidine 26 is formed in the reaction o f the 6-amino-uracile 23 with the aminal 3a. In an unexpected reaction the 1,2-bis(cyano-dialkylaminomethylene)-cyclobutanes 28a-d result fr om the action of trimethylsilylcyanide on the aminals 3e-h. The corres ponding reaction with trimethylsilylisothiocyanate affords the vinylog ous amidinium thiocyanates 34a,b. In the reaction of trimethylsilylazi de and the aminals 3 are produced the 4-(dialkylaminomethylene)-4H-1,2 ,3-triazoles 38.