Orthoamides. L. Contribution to the chemistry of propiolaldehydaminales - Synthesis and transformations to push-pull-substituted buta-1,3-dienes, cyclobutanes, vinylogous amidinium salts and 1,2,3-triazoles

Article abstract of DOI:10.1002/prac.19973390130

Tert-butylaminalester 5 reacts with terminal alkynes to give aminals of 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)acetonitrile 8 and terminal alkynes in the presence of sodium hydride. The nitrile 8 is also useful for the preparation of the bis-aminal of acetylenedialdehyde 6. The aminal 3e can be transaminated by heating with secondary amines to give the aminals 3f-i. The aminals 3a-i react with strong CH₂-acidic compounds (pK_a between 9 and 14) to give the 1-dialkylamino-1,3-butadienes 10. The isomeric 1-dialkylamino-butadienes 18 can be obtained from the condensation of the CH-acidic cinnamic acid derivatives 19 with dimethylformamidedimethylacetal. CH and NH-acidic compounds as cyanacetamide react with the aminals 3c,e exclusively with the acidic methylene group to produce the enamines 10h,t. The acylformamidine 21 can be obtained from 10t and tert-butylaminalester 5. The pyridone 22 is accessible from the condensation product 10h by thermal cyclization. The pyrido[2,3-d]pyrimidine 26 is formed in the reaction of the 6-amino-uracile 23 with the aminal 3a. In an unexpected reaction the 1,2-bis(cyano-dialkylaminomethylene)-cyclobutanes 28a-d result from the action of trimethylsilylcyanide on the aminals 3e-h. The corresponding reaction with trimethylsilylisothiocyanate affords the vinylogous amidinium thiocyanates 34a,b. In the reaction of trimethylsilylazide and the aminals 3 are produced the 4-(dialkylaminomethylene)-4H-1,2,3-triazoles 38. Johann Ambrosius Barth 1997.