Amidines tandem reaction

Chang, S., Lee, M., Jung, D.Y et a/. (2006) Catalytic one-pot synthesis of cyclic amidines hy virtue of tandem reactions involving intramolecular hydroamination under mild conditions. Journal of the American Chemical Society, 128, 12366 12367. 

Chang et al. reported a mild tandem intramolecular hydroamination of yne amines to form an endo-adduct intermediate, which reacts with electron-deficient azides to produce cyclic amidines <06JA12366>. Selected examples of an interesting synthetic route to tropene derivatives 165 via a dual hydroamination strategy is shown below. This one-step reaction makes use of a palladium catalyst and takes place by sequential intermolecular hydroamination of cycloheptatriene with aryl, heteroaryl, and primary alkyl amines to generate intermediate 166, followed by transannular intramolecular hydroamination <06JA8134>. 

Conversion of 1,3-diketones 315 into 2-substituted 7,8-dihydroquinazolin-5(6//)-ones 569 by a reaction with substituted amidine hydrochloride and dimethylform-amide dimethyl acetal (DMF-DMA) was achieved under MWI and in aqueous media. The aqueous conditions led to an environmentally friendly work-up. Compounds 569 were obtained in 21-68% yields within 2 min (Scheme 112). The reaction is a tandem addition-elimination/cyclodehydration that took place via a Michael addition of the terminal amino group of the substituted amidine to form intermediate 568, followed by an intramolecular cyclodehydration to give dihydroquinazoli-none derivatives 569 (02S1669). 

Tandem oxidation processes have also been applied to five-and six-membered heterocycle synthesis. New examples of six-membered rings include pyrimides and p)mdines. In one approach, an cK-arylpropargyl alcohol is oxidized to the corresponding ynone, which then reacts with ethyl a-aminocrotonate or an amidine to afford pyridines or p)Timidines, respectively (eqs 105 and 106). In both cases, the reactions were limited in scope, but the former was subsequently inproved by implementation of 8-keto esters and ammonium acetate in place of the a-amino cro-tonate s)mthon (eq 107). ... 

Spirocyclic sugar isoxazolidinones such as (34) have been synthesized by tandem Michael addition - 1,3-dipolar cycloaddition reactions as shown in Scheme 5. Reduction of adduct (34) yielded the spirocyclic glycosylamine derivative (35). The syntheses of 8-

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