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

Rhodium-Catalyzed Formal C-O Insertion in Carbene/Alkyne Metathesis Reactions: Synthesis of 3-Substituted 3 H-Indol-3-ols

An efficient and novel rhodium-catalyzed formal C-O insertion reaction of alkyne-tethered diazo compounds for the synthesis of 3 H-indol-3-ols is described. A type of donor/donor rhodium carbene generated in situ via a carbene/alkyne metathesis (CAM) process is the key intermediate and terminates in a unique transformation different from donor/acceptor carbenoids. In addition, ¹⁸O-labeling experiments indicate that intramolecular oxygen-atom transfer from the amide group to the carbon-carbon triple bond occurs during this transformation.

Rhodium-catalyzed tunable oxidative cyclization toward the selective synthesis of α-pyrones and furans

The Rh^III-catalyzed tunable oxidative cyclization of readily availableN-tosylacrylamides and diazo compounds toward the selective synthesis of fully substituted furans and α-pyrones is presented.

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones - First evidence for the 1,3-oxathiole-thiocarbonyl ylide interconversion

Acyclic diazodicarbonyl compounds react at room temperature with cycloaliphatic thioketones, e.g. 2,2,4,4-tetramethyl-3-thioxocyclobutanе-1-one and adamantanethione, via a cascade process in which the key step is a 1,5-electrocyclization of the intermediate thiocarbonyl ylide leading to tetrasubstituted spirocyclic 1,3-oxathioles. The most reactive diazodicarbonyl compound was diazoacetylacetone. In the case of dimethyl diazomalonate competitive 1,3-electrocyclization yielded the corresponding thiirane at elevated temperature, which after spontaneous desulfurization produced a tetrasubstituted alkene. To explain the observed temperature dependence of the main reaction product type obtained from dimethyl diazomalonate and 2,2,4,4-tetramethyl-3-thioxocyclobutanе-1-one as well as to verify reversibility of the thiocarbonyl ylide and 1,3-oxathiole interconversion, the calculations of the energy profile for the transformation of 1,3-oxathiole to alkene were performed at the DFT PBE1PBE/6-31G(d) level.

Rhodium carbene routes to oxazoles and thiazoles. Catalyst effects in the synthesis of oxazole and thiazole carboxylates, phosphonates, and sulfones

Dirhodium tetraacetate catalyzed reaction of alpha-diazo-beta-keto-carboxylates and -phosphonates with arenecarboxamides gives 2-aryloxazole-4-carboxylates and 4-phosphonates by carbene N-H insertion and cyclodehydration. In stark contrast, dirhodium tetrakis(heptafluorobutyramide) catalysis results in a dramatic change of regioselectivity to give oxazole-5-carboxylates and 5-phosphonates. Alpha-diazo-beta-ketosulfones behave similarly and give 5-sulfonyloxazoles upon dirhodium tetrakis(heptafluorobutyramide) catalyzed reaction with carboxamides. The analogous reactions of thiocarboxamides give the corresponding thiazole-5-carboxylates, -phosphonates, and -sulfones.

Reaction of 2,3-Allenoates with TsNBr2 in the Presence of Base: A Facile Highly Stereoselective Synthesis of (1E,2E)-3-Bromo-4-oxo-N‘-tosyl-2-alkenoxylimidic Acid Ethyl Esters

A novel reaction pathway of 2,3-allenoates with an electrophile (TsNBr2) in the presence of K2CO3 to produce (1E,2E)-3-bromo-4-oxo-N'-tosyl-2-alkenoxylimidic acid ethyl esters is reported. The reaction proceeds in a highly stereoselective fashion. A plausible mechanism to rationalize this reaction is also proposed.