Recent Advances in the Cycloaddition Chemistry of Isomünchnones and Thioisomünchnones, an Under-Utilized Class of Mesoionic Compounds

Design and Synthesis of a Conformationally Rigid Mimic of the Dihydropyrimidine Calcium Channel Modulator SQ 32,926

“…The synthetic strategy towards the polycyclic DHPM derivative 3 is based on an intramolecular 1,3-dipolar cycloaddition reaction of an o-alkenylaryl-tethered dihydropyrimidine-fused isomünchnone dipole ("cyclization-cycloaddition cascade", see Scheme 1 [13]). In recent publications we have described model studies dealing with bimolecular and intramolecluar dipolar cycloaddition reactions of a variety of dihydropyrimidine-fused mesomeric betaines, including 1,3-thiazolium-4-olates, 1,3-oxazolium-4-olates, and cross-conjugated heteroaromatic 1,3-thiazinium betaines [14].…”

Organophosphorus Compounds, Part 149. Preparation of 1,3-Oxaphospholes by Transition Metal-Catalyzed Reactions of α-Diazo-β-dicarbonyl Compounds with tert-Butylphosphaacetylene

“…12,13 It has found particularly frequent use for the in situ generation of carbonyl ylides. 14,15 Thus, the first step in the synthesis of 1,3-oxaphospholes described here is most probably the formation of the reactive rhodium carbenoid 11 from the diazo compound 7 under the action of rhodium(II) acetate. A plausible explanation for the further course of the reaction is provided by the following sequence.…”

Intramolecular cyclizations of N-acyliminium ions with pyridine rings

“…Earlier studies in our laboratory showed that 1,3-oxazolium-4-oxides (isomünchnones) 21 can be generated by the rhodium(II)-catalyzed cyclization of a suitable diazo imide 20 (Scheme 4). 15 This type of mesoionic ylide corresponds to the cyclic equivalent of a carbonyl ylide and was found to readily undergo [4+2]-cyclo-addition with suitable dipolarophiles. 16 …”