Enamidines

In the synthetic route starting with enamidine (238) (398), its metalation followed by alkylation in the presence of TMEDA or pentynyl cuprate gave the... 

Enamidines are cleaved to aldehydes by hydrazinolysis with 1,1-dimethylhydrazine and cleavage of the resultant hydrazone (equation II). Alternately, enamidines can be converted by aluminum amalgam to the corresponding N-methyl enamine, which is cleaved by dilute acid. 

Enamidines can be converted to homologated ketones by alkylation of the anion (t-butyllithium) followed by hydrazinolysis and subsequent cleavage (equation III). 

Eleutherin, 21 Enamidines, 347—348 NB-Enantrane, 229 NB-Enantride, 229-230 Endoperoxides, 171-172, 504 Endothiopeptides, 55 Ene-y-lactones, 71... 

Enamidines (2). Lithiation of 1 followed by treatment with aldehydes or ketones results in Peterson olefination to give a mixture of isomeric enamidines (2) in good yield. These enamidines can be used to convert the carbonyl compounds used in (heir preparation to homologated amines, aldehydes, and ketones. Conversion to a mclhylaminc involves reduction with sodium borohydride (pH 6) to an aminal, which is then hydrolyzed by dilute acid. The sequence can be carried out from 1 without isolation of any intermediates (equation I). 

A novel method has been reported for the elaboration of carbonyl compounds, which is discussed in Section 2.1.4.2. ° However, one of the examples falls into the present category the transformation of cyclohexanone to keto alcohol (4), via enamidine (1 equation 1). Treatment of (1) with r-butyllithium effects regioselective deprotonation of the vinylic hydrogen to give (2), which adds to propanal to give (3). Hydrolysis then provi s keto alcohol (4). ° ... 

Enamidine derivatives (177) afford pyridinimines (178 31-75%) in the Vilsmeier-Haack Reaction. ... 

Enamidines. A suspension ofN- trans 4 nitr osty ry Isulf ony 1) benz -amidine in acetone stirred 1 hr. with aq. NaOH N-(/r n -4-nitrostyryl)benzamidine. Y 96%. - Formation of enamidines is favored by electron-withdrawing substituents in the styryl ar. ring. Org. Chem. 59, 3080 (1974). 

Ripa, L., Hallberg, A. (1996) Controlled Double-bond Migration in Palladium-catalyzed Intramolecular Arylation of Enamidines. J. Org. Chem. 61 7147-7155. 

Scheme 7.9 Intramolecular Mizoroki-Heck arylation of enamidine 20 and intermediates observed by ESI-MS.

Entry Arylboronic acid Enamidine Catalytic system Species observed by ESI-MS... 

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