Nitroethylene: A Stable, Clean, and Reactive Agent for Organic Synthesis

Article abstract of DOI:10.1021/jo01295a003

Contrary to current belief, nitroethylene is a stable reagent and holds promise as a useful and reactive synthon.Nitroethylene can be prepared in 20-25-g lots, and standard, refrigerated solutions in common solvents provide a good and ready source of the reagent.The reagent purity can be easily monitored by titration against tetraphenylcyclopentadienone (tetracyclone) coupled with the isolation of the colorless crystalline adduct.With reactive substrates, nitroethylene reacts with greatest ease at low temperatures, leading to functionalized systems having potential for further elaboration.With systems that require heating, the limited stability of nitroethylene itself complicates the course of the reaction.Cyclopentadiene, 5-<(benzyloxy)methyl>cyclopentadiene, 5-(methoxymethyl)cyclopentadiene, 5-(1,3-dithianyl)cyclopentadiene, 5-(trimethylsilyl)cyclopentadiene, and spiroheptadiene readily gave (4 + 2) adducts with nitroethylene, each possessing attraction as a synthetic intermediate.Adducts from furan and acetoxyfulvene undergo rearrangement via ? cleavage.The (4 + 2) adduct from 9-diazofluorene spontaneously extrudes nitrogen, leading to spironitrocyclopropane.Indole readily undergoes Michael addition to give 80percent 3-(nitroethyl)indole and 15percent of novel bis adduct.The 2,6 Michael adduct arises with 1-morpholinocyclohexene, and β-pinene undegoes an ene reaction with nitroethylene.Novel 2-nitroethyl phosphonates, useful in Wittig-Horner reactions, arise from nitroethylene and phosphites in tert-butyl alcohol.