Formation of Three Bonds

The formation of pyridazines from three components was reviewed in CHEC-I and the most common examples are of reaction of an a-diketo compound, a hydrazine, and an ester or nitrile containing an adjacent activated methylene group, to give compounds like 4-cyano-3(2//)-pyr-idazinone or 3-amino-4-cyanopyridazines. A different type of example is illustrated by the condensation of a nitrostyrene with two equivalents each of methyl acetoacetate and hydrazine hydrate (Equation (36)) to give the pyridazine (126) in good yield 87JHC23 . 

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The formation of pyridine derivatives from a, P-unsaturated aldehydes and ammonia involves formation of three bonds during the ring synthesis. For example, with an a, P-unsaturated aldehyde, both 2,5-substituted as well as 3,4-substituted pyridines can be obtained, depending on whether a 1,2- (eq. 17) or 1,4-addition (eq. 18) occurs with ammonia. Reactions are performed in the vapor phase with catalysts. 

Primary syntheses involving formation of three bonds... 

By Formation of Three Bonds from [3+2+1] Atom Fragments. 249... 

By formation of three bonds from [4+1+1] atom fragments 155... 

Formation of three bonds starting from [8+2] fragments 309... 

Formation of three bonds Two N-S bonds and one C-C bond 5.09.9.1.7(i) Formation by reaction of potassium cyanide with sulfur dioxide... 

CONSTRUCTION OF PYRROLE RINGS BY PROCESSES INVOLVING FORMATION OF THREE BONDS... 

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