Orthoamides and iminium salts, LXXXIX. Reactions of N,N,N ',N ',N '',N '',N ''',N '''-octamethylacetylene-bis(carboxamidinium) tetrafluoroborate with nucleophilic reagents - new methods for the preparation of amidinium salts and ketene aminals

摘要

The acetylene-bis(carboxamidinium) salt 4 dehydrates carboxylic acids to the corresponding anhydrides, as the byproduct 2-oxo-but-2-en-amidinium salt 6b was isolated. Aromatic hydroxy compounds and 2-furyl-methylmercaptan add to the triple bond of the salt 4 to give 2-aryloxy-and 2-alkylmercapto-but-2-enebis(amidinium) salts 7-9. According to this reaction principle, 2-organoamino-buten-2-ene-bis(amidinium) salts 10 and 11 were prepared from 4 and primary and secondary amines, whereas 4-chlorobenzhydrazide reacted with 4 to give the imidazole-3-carboxamidinium salt 13. The reaction of CH2-acidic compounds as malononitrile or ethyl cyanoacetate with the bis(amidinium) salt 4 affords 2-cyanomethylene-but-3-enamidinium salts 15. With the CH-acidic diethyl 2-bromomalonate, compound 4 undergoes a Michael-initiated ring closure cyclopropenation reaction with further ring opening by the released Br-to the corresponding 2-diethoxycarbonylmethylene- 3-bromo-but-3-enamidinium salt 18. Unlike cyclopentadiene and furane, the reaction of N-methylpyrrole and bis(amidinium) salt 4 does not lead to Diels-Alder [4 + 2] cycloadduct but to the Michaeltype 1:1 adduct 20. Pyrrole-and thiophene-2-carboxamidinium salts 23-25 can be prepared from compound 4 and esters of glycine, N-methylglycine (sarcosine), and mercaptoacetic acid, respectively. The derivatives of quinoxaline-2-carboxamidinium salts 29 are accessible from aromatic 1,2-diamines and compound 4. The reaction of the CH2/NH-acidic cyanoacetamide with the bis(amidinium) salt 4 produced the 3-pyrroline-2-on derivatives 33.