Efficient Synthesis of Resin-Bound α-TMSdiazoketones and Their Use in Solid-Phase Organic Synthesis

Cyclic and acyclic sulfonimides in reactions with Rh(ii)-ketocarbenoids: a new access to chemoselective O-functionalization of the imidic carbonyl groups

Catalytic decomposition of diazoacetylacetone, diazoacetoacetic, diazomalonic, and diazoacetic esters using dirhodium tetraacetate in the presence of isothiazol-3(2H)-one 1,1-dioxides and a number of N-(arenesulfonyl)carboxamides in solutions of methylene chloride or dichloroethane gives rise to O-alkylation of the imidic carbonyl groups by Rh(II)-carbenoids and the formation of O-alkylimidates as the final products. The reaction proceeds with high chemoselectivity via carbonyl ylides and offers a powerful method for the synthesis in good yields of the imidates with polyfunctional O-alkyl groups. On the basis of X-ray analysis and 1H- and 13C-NMR studies it was shown that the resulting acyclic O-alkylimidates have the E-configuration in the solid state and in solution. Unlike acyclic analogues, the cyclic carbonyl ylide derived from substituted diazosaccharin by intramolecular cyclization of the appropriate diketocarbenoid is capable of reacting with DMAD in a 1,3-cycloaddition process.

Cu(i)-carbenoid- and Ag(i)-Lewis acid-catalyzed asymmetric intermolecular insertion of α-diazo compounds into N–H bonds

Chiral Cu(I)-bisoxazoline- and Cu(I)-PN-complexes were found to catalyze the intermolecular insertion of alpha-diazo compounds into N-H bonds. The insertion reactions proceed with enantioselectivities of up to 28% ee for the different alpha-diazo acetates into one of the N-H bonds of different amines. Analogous chiral Ag(I) complexes were found to give higher enantioselectivities of up to 48% ee, however, lower yields were obtained. There are indications, that the Ag(I)-mediated reactions follow a different reaction mechanism compared to the Cu(I)-catalyzed insertions. It is demonstrated that different alpha-amino acid derivatives can be obtained via this approach in good yields and with low to moderate enantioselectivities. However, the results obtained are the highest asymmetric inductions obtained for an intermolecular N-H insertion via chiral carbene complexes or chiral Lewis acid catalysis.

Solid-phase rhodium carbenoid N-H insertion reactions: the synthesis of a diverse array of indoles

A solid-phase synthesis of an array of indoles is reported. The key step in our approach involves a N-H insertion reaction of N-alkylanilines into a highly reactive polymer-bound rhodium carbenoid intermediate to yield the corresponding alpha-arylamino-beta-ketoester. These insertion products were then treated under acid-catalyzed cyclodehydration conditions to yield a series of polymer-bound indole esters, which were subsequently cleaved from the resin under Lewis acid-promoted amidation conditions to yield the desired indoles in good yields and with excellent purities.

Rhodium carbenoid N-H insertion reactions of primary ureas: solution and solid-phase synthesis of imidazolones

[reaction: see text] The solution and solid-phase synthesis of imidazolones is reported. The key step for the preparation of these compounds is the N-H insertion reaction of primary ureas into highly reactive rhodium carbenoid intermediates. Typically, a soluble or support-bound alpha-diazo-beta-ketoester is treated with a rhodium carboxylate catalyst in the presence of a primary urea to give the corresponding N-H insertion product. Subsequent acid-catalyzed cyclodehydration of these insertion products affords the desired imidazolone products.

Solid-phase rhodium carbenoid reactions: an N-H insertion route to a diverse series of oxazoles

[reaction: see text] The solid-phase synthesis of a series of oxazoles is described. The key step in the construction of these molecules involves the rhodium-catalyzed decomposition of polymer-bound alpha-diazo-beta-ketoesters. These reactions are performed in the presence of primary amides and yield the corresponding N-H insertion products. Subsequent cyclodehydration of these alpha-(acylamino)-beta-ketoesters provides the corresponding resin-bound 2,5-disubstituted oxazoles, which are further elaborated during cleavage from the resin.