Isocyanides amidine synthesis

Keimg et al. describes the optimization of 2-imino-piperazines using Lewis acids to catalyze the multicomponent a-amino amidine synthesis to make piperazines 39 (Scheme 6) [26]. A, Af -(jimethylethylenediamine 36 was used with an aldehyde 37 and isocyanide 38 in methanol with scandium (III) trifluoromethane sulfonate (Sc(OTf)3) as a catalyst to obtain the piperazine 39 in 57% yield. 

Based on this concept, Whitby and co-workers [110] reported an interesting palladium-catalyzed three-component synthesis of aromatic and heteroaromatic amidines 133 starting from unsaturated halides, amines, and t-butylisocyanide (Scheme 8.53). The catalytic cycle for this iminocarbonylative coupling reaction is analogous to the reactions incorporating carbon monoxide-isoelectronic with isocyanides-as the third partner [111]. 

X -systems, and other low coordination phosphorus species, in particular phosphenium ions, R2P , and phosphinidenes, RP . The reactions of phosphenium ions with isocyanides, 1,3-dienes and o-quinones, and amidines, have been investigated. The coordination chemistry of phosphenium ions also continues to stimulate interest.The thermal decomposition of phosphirene and phosphirane P-complexes provides a new approach for the synthesis of terminal phosphinidene complexes, e.g., (180), which can be trapped with a variety of reagents. Evidence of the formation of surface phosphinidene intermediates has been adduced in the heterogeneous dechlorination of alkyldi-chlorophosphines by magnesium metal at 600K. ... 

MW irradiation can also accelerate the synthesis of fused 3-aminoimidazoles 37 in a similar reaction to that described above but now in MeOH as solvent. Libraries of 37 were produced by Tye et al. (ten compounds) [73] and Zhang et al. (sixty compounds) [74] via a three-component reaction of heterocyclic amidines with isocyanides and aldehydes using a catalytic amount of Sc(OTf)3 (Scheme 17.27). 

Other catalysts, such as ZrCl [16] and cellulose sulfuric acid (CSA) [17], have been also reported to activate the Ugi-3CR. In this context, Khan et al. have described the nse of bromodimethylsulfonium bromide (9) (BDMS) as catalyst for the synthesis of a-amino amidines 10 by the reaction of aromatic aldehydes, aromatic amines, and isocyanides (Scheme 7.4) [18]. 

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