5-Keto-13-dienamines

Bridged l,6,6aA -trithiapentalenes 608 are synthesized by the reaction of keto dienamines 607 with P2SS or LR (Equation 31) <2001SL1129>. 

In the same manner bicyclic fully conjugated dienamines underwent autooxidation in air giving mainly the <5-keto products. Addition of a catalytic amount of cupric salts (as well as ferric salts) enhanced the oxidation rate and increased the yields37 (Scheme 22). 

The same was observed for steroidal dienamines having a carbonyl group at C-17157 and for enamino esters which were reduced by LiAlH4 at the keto and ester functions, respectively, leading in the latter case to saturated pyran and furan derivatives158,159 (Scheme 111). 

Oxidation. P-Enamino carboxamides derived from cyclic p-keto amides are oxidized by Mn(OAc)j-Cu(OAc)2 to give enones, dienamines, or aniline derivatives, depending on the ring size. 

Later, Melchiorre and coworkers accomplished a challenging direct vinylogous aldol reaction of 3-methyl-2-(yclohexen-l-one with a-keto esters utilising a bifunctional primary amine-thiourea. Catalyst 48 based on the (l/ ,2/ )Kiiphenylethylene-l,2-diamine backbone combined with benzoic acid as cocatalyst promoted the reaction by means of a concomitant activation of both reacting partners (see TS in Scheme 19.55), the ketone via dienamine catalysis and the ester via hydrogen-bonding interactions (Scheme 19.55). 

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