Dihydro-2,2-dimethyl-5,5-bis propylthio 1,3,4-oxadiazole

Cycloaddition Reactions. The reaction of pyridinium, iso-quinolinium, and benzimidazolinium 7V-ylide with fluorovinyl tosylate 1 gives cyclic monofluorinated adducts in moderate yield (eq 6). The reaction mechanism is thought to involve initial 1,3-dipolar cycloadditon of the TV-ylide to 1, followed by elimination of both tosic and hydrofluoric acid.  

Ichikawa, J. Wada, Y. Fujiwara, M. Sakoda, K., Synthesis 2Wi2,1917. 

Knochel, P. Jones, P., Ot anozinc Reagents, Oxford Univarsity Press New York, 1999. 

Patrick D. O Connor University of Auckland, Auckland, New Zealand 

Physical Data solid at —78 °C, thermolysis occurs at 0 °C and above. 

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Cycloaddition with Vinyl Isocyanate. When a large excess of 2,5-dihydro-2,2-dimethyl-5,5-bis(propylthio)-1,3,4-oxadiazole carbene precursor is added rapidly in refluxing benzene to a vinyl isocyanate, two equivalents of carbene add to the substrate prior to ring closure, leading to a six-membered adduct (eq 3). However, no carbene insertion into the amide N-H bond occurs. This phenomenon is not observed with the dimethoxy carbene. ... 

Addition of 2,5-dihydro-2,2-dimethyl-5,5-bis(propylthio)-l,3,4-oxadiazole in refluxing benzene and an aryl isocyanate releases the bis(propylthio)carbene in situ which then adds easily to the aryl isocyanate to yield a substituted isatin with the ketone functionality protected as a thioacetal (eq 4)7 Ring closure also occurred when the 2,5-dihydro-2,2-dimethyl-5,5-bis(propylthio)-1,3,4-oxadiazole carbene precursor was added to 1-naphthyl isocyanate in refluxing acetonitrile (eq 5)7 Formation of thioacetal protected isatin products are unique to the bis(propylthio)carbene as other nucleophilic carbenes added to aryl isocyanates afforded only modest yields of hydantoin products. ... 

F 4] Cycloaddition with Vinyl Isocyanates. Upon thermolysis in refluxing benzene, 2,5-dihydro-2,2-dimethyl-5,5-bis-(propylthio)-l,3,4-oxadiazole yields the bis(propylthio)carbene precursor, which reacts as a 1,1-dipole equivalent in [1 -E 4] cycloaddition reactions with various vinyl isocyanate substrates leading to highly functionalized adducts such as hydroindolones (eq 1). Reductive desulfurization with Raney nickel yields the enamide or the fully reduced system (eq 2). Cyclohexyl isocyanide also behaves as a 1,1-dipole equivalent in [1 -E 4] cycloadditions with vinyl isocyanates, however the adducts are less functionahzed. ... 

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