Lin Zhi

Cycloalkenone formation by the intramolecular addition of a α-diazoketone to an acetylenic pi-bond

Abstract Treatment of several ortho alkynyl substituted α-diazoacetophenone derivatives with rhodium (II) acetate results in intramolecular addition to the acetylenic pi-bond to give a transient cyclopropene which spontaneously rearranges to a vinyl carbene intermediate.

Synthesis of exo and endo-brevicomin via the rhodium acetate catalyzed cycloaddition reaction of 1-diazo-2,5-hexanedione

Abstract Treatment of 1-diazo-2,5-hexanedione with rhodium (II) acetate in the presence of various aldehydes affords the 6,8-dioxabicyclo[3.2.1]octane ring system in high yield.

Cyclic carbonyl ylide formation from the rhodium (II) acetate catalyzed reaction of 1-diazoalkanediones

Abstract Treatment of 1-diazoalkanediones with rhodium (II) acetate results in cyclization of the intermediate rhodium carbenoid to give a cyclic carbonyl ylide which readily undergoes bimolecular dipolar cycloaddition with various dipolarophiles.

Azomethine ylide generation via the dipole cascade

Abstract A series of N-acyl 2-diazo-3-oxobutanoates, when treated with a catalytic quantity of a rhodium(II) carboxylate, were found to afford substituted pyrroles derived from an azomethine ylide intermediate. The initial reaction involves generation of the expected carbonyl ylide dipole by intramolecular cyclization of the keto carbenoid onto the oxygen atom of the neighboring amide group. The primary cycloadduct undergoes a subsequent rearrangement-fragmentation reaction to give the pyrrole derivative. When the α-position of the α-diazoketone was blocked with two methyl groups, the rhodium(II)-catalyzed cycloaddition with dimethyl acetylenedicarboxylate led to the carbonyl vlide cycloadduct in high yield. MNDO calculations show that the cyclic carbonyl ylide derived from ethyl 2-diazo-4-dibenzoylamino-3-oxobutyrate is 3.3 kcal lower in its heat of formation than the corresponding azomethine ylide. This thermodynamic difference in stability of dipoles nicely accounts for why the carbonyl ylide cycloadduct is the major product from the rhodium(II) catalyzed reaction of ethyl 2-diazo-4-dibenzoylamino-3-oxobutyrate.

Rhodium(II) Catalyzed Cyclization of Diazo Thiocarbonyl Compounds for Heterocycloic Synthesis

The mesoionic thioisomuchnone system was prepared from the rhodium(II) acetate catalyzed cyclization of a diazothioamide and was found to undergo smooth 1,3-dipolar cycloaddition with N-phenylmaleimide. In contrast to this system, the rhodium(II) reaction of an α-diazo-β-oxo ester containing a thiocarbonyl group produced a cyclic thiocarbonyl ylide which extruded sulfur from a transient episulfide intermediate

Photochemical rearrangement of 8-oxabicyclo[3.2.1]oct-6-en-2-ones

Abstract Irradiation of 8-oxabicyclo[3.2.1]oct-6-en-2-ones results in a 1,3-acyl rearrangement. The initial photoproduct undergoes a subsequent reaction involving hydrogen transfer followed by intramolecular cycloaddition of a ketene intermediate.