Fluorenone oximes

A mixture of 8.5 g. (0.047 mole) of fluorenone (p. 163), 6.6 g. (0.95 mole) of hydroxylamine hydrochloride, and 80 ml. of 70% ethanol is refluxed for 3 hours. The ethanol is removed by distillation and the residue treated with excess water. The resulting solid product is removed by filtration and washed thoroughly with water. The solid is recrystallized from ethanol with a charcoal treatment to give an 82% yield of the oxime, melting at 192-193°. 

---

The second-order rate constant for the methylation of sodium 9-fluorenone oximate in 33.5% acetonitrile/66.5% t-butyl alcohol solution was found to decrease with increasing concentration of the salt, suggesting an equilibrium (13) between the reactive free anion [109] and the less reactive ion pair [110]... 

Methylation of sodium fluorenone oximate in 33.596 acetonitrile and 66.5% t-butyl alcohol at 25°C in the presence of NaBPh4 or dibenzo-18-crown-6 111] ... 

Ambident reactivity was shown by oximate anions normally, Oarylation predominated over N-arylation, with ratios of oxime ethers to nitrones ranging from 9 1 (for the benzophenone oxime anion) to 1.7 1 (for the fluorenone oxime anion) [77]. The arylation of two heterocyclic oximes was performed under mild conditions and led mainly to the corresponding oxime ethers which served as good precursors for the generation of unstable aryl fulminates, ArONC [79,80],... 

Seventy grams (1.07 gram atoms) of zinc dust is added in small portions under a reflux condenser to a stirred solution of 40 g. (0.205 mole) of fluorenone oxime (p. 164) in 267 ml. of acetic acid and 13 ml. of water. The rate of addition of the zinc is such as to maintain an even, gentle reflux. The mixture is then refluxed for another hour by the application of heat, and this is followed by the addition of 400 ml. of water. The mixture is filtered and the residue extracted with 200 ml. of hot 5% acetic acid. The solution thus obtained is cooled and filtered, and the filtrate is mixed with an equal volume of concentrated hydrochloric acid and held at 0° for 12 hours. The precipitated amine hydrochloride is removed by filtration and treated with excess ammonium hydroxide solution, and the resulting free base is recrystallized from petroleum ether to give a 90% yield of 9-aminofluorene, m.p. 62-63 . 

Ketoximes are deprotonated by EGB to the oxime anion, which requires a more negative potential for its reduction. Fluorenone oxime gave for n = 1 unchanged oxime, fluorenone (hydrolysis of fluorenone imine), fluorenone imine, and some 0-butylfluorenone oxime, presumably formed by attach of the oxime anion on TBABF4 [62]. 

Fluorenone oxime was recovered unchanged after being heated with PPA at 120°, but at 180° it was rearranged in almost quantitative yield (Conley )- Conley found PPA to be a superior solvent-catalyst for the Schmidt rearrangement. He added sodium azide in portions to a mixture of a diaryl, aryl-alkyl, symmetrical or unsymmetrical ketones with 15-20 parts of PPA at a temperature in the range 25-75° until evolution of nitrogen ceased, and obtained amides in yields mainly of 80-90%. Doorenbos and Wu studied the conversion of cholestanone and... 

A biological analogue of the above reaction is known. Aryl sulphotransferase isozyme I readily sulphates 9-fluorenone oxime (35) at pH 7-9 to form the sulphate ester, which then rearranges non-enzymically to phenanthridone (equation 19)65. This Beckmann rearrangement accounts for only a part of the transformation of the oxime 35. 

One of the strongest pieces of evidence against the formation of the carbene radical anion comes from an experiment using a nitrogen-15 labelled diazofluorene. The latter was prepared by reacting fluorenone oxime labelled 88% with nitrogen-15 with chloramine (equation 24). 

Sodium 9-fluorenone oximate, as dissociated ions (114), is alkylated to the extent of 65% at O and 35% at N. When existing as ion pairs the oximate reacts to give 30% 0-methyl product. In the presence of a crown ether the oximate ion undergoes almost exclusive (95-99%) 0-methylation with MeOTs and 0/N-methylation (65 35) with Mel (115). Addition of NaBPh4 to suppress dissociation of the sodium oximate reduces the alkylation with both MeOTs and Mel to nearly the same rate and gives essentially an identical proportion (ca. 43 57) of 0/N-alkylation. Under such conditions, the two heteroatoms are of approximately the same hardness. 

Fluorenone oximes from fluorenes s. 16, 229 Phosphoric acid HgPO ... 

Nitro-phenyl]-benzBeIenazoI 27 II 39. CuH,N,0 2-Nltro-fluorenon-oxim 7 II 409. 

Dimethyl sulfoxide, fluorenone oxime, and p-nitrobenzonitrile added in turn to a soln. of Na in methanol, and stirred 24 hrs. at room temp. product. Y 73%. F. e. s. J. B. Baumann, Synthesis 1975, 782. 

This has been achieved using a copper-catalyzed coupling between vinylboronic acids and fluorenone oxime [126]... 

Bucher, G., Scaiano, J. C., Sinta, R., Barclay, G., and Cameron, J., Laser flash photolysis of carbamates derived from 9-fluorenone oxime, /. Am. Chem. Soc., 117, 3848,1995. 

---