Aminomalonate complexes

A very closely related decarboxylation reaction which is accelerated by metal ions is observed with aminomalonate complexes (Fig. 5-24). Once again, the initially-formed product is in the enolate form. 

Snyder and Smith prepared diethyl acetamidomalonate in 40% yield by reduction of diethyl isonitrosomalonate in ethanol over palladium on charcoal followed by direct acetylation of diethyl aminomalonate in the filtrate with acetic anhydride. Ghosh and Dutta used zinc dust instead of palladium. A modification using Raney nickel is described by Akabori et al. Shaw and Nolan reported a 98% yield by conversion of diethyl oximino-malonate-sodium acetate complex. 

With the same protocol, a heterocyclic dibenzoate 86 derived from furan in one step has been efficiently desymmetrized to provide facile entry to either D or L nucleosides (see Scheme 8E.10). As depicted in Scheme 8E.10, the catalyst derived from ligand 71 gave rise to high enantioselectivities in the alkylation with both a purine 83 and a pyrimidine 87 [62], Subsequent allylic alkylations with an achiral ligand introduced the tartronate and aminomalonate moieties to furnish enantiomerically pure Ci s-2,5-disubstituted-2,5-dihydrofurans 89 and 91, respectively. Only six steps from furan were required to synthesize the alio and talo isomers of the nucleoside skeleton of the polyoxin-nikkomycin complexes. It should be noted that the corresponding enzymatic desymmetrization of substrate 86 is impossible because the product is labile. 

More complex nucleophiles can be reacted with alkynyl(phenyl)iodonium salts as well. For example, protected aminomalonates (50) and 18 give the corresponding alkynylmalonates 51 in 30-90% isolated yields (equation 19). Likewise, a variety of dicarbonyl enolates 52-54 react with 55 to give alkynyl products 56-58 (equations 20-22). These reactions may be looked upon as alkynylations or, in other words, the triple-bond analogs of the well-established alkylation reactions. Unfortunately, they only work with soft nucleophiles such as 52-54 (OTs, PhC02 PhsP, etc.). Nucleophiles such as RO, or simple enolates, do not seem to work. 

The a-aminomalonate anion reacts with ra 5-[Co(en)2Cl2] in the presence of triethylamine to give a-diamine and carbinolamine complexes/ " Reaction in aqueous solution gives the carbinolamine complex in the presence of air, but under N2 the a-diamine is preferentially formed. The complexes (11) and (12) have been characterized by visible spectra, and CNMR, and the crystal structure of the complex (11) determined. 

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