The cyanation of chlorobenzene catalyzed by Ni(PPh3)n, which was generated in situ from NiBr2(PPh3)2–Zn–PPh3(Ni : Zn : P=1 : 3 : 2 molar ratio), was at first examined with various MCN (M=K, Na)–solvent systems by three procedures in order to clarify the conditions under which the reaction occurs. The effects of the systems and the procedures on the reaction were remarkable. It was observed that the cyanide ion has an inhibitory action on both the reduction of Ni(II) and the oxidative addition of the halide to Ni(0). However, when such MCN–dipolar aprotic solvent systems as KCN–HMPA, KCN or NaCN–MeCN, which give low cyanide concentrations, were used, the reaction readily took place at 50–60 °C without reducing Ni(II) prior to the addition of MCN and adding MCN slowly. Various Y-substituted chlorobenzenes, except for those with Y=o-Cl, o-CN, and m-NO2, were cyanated to give the corresponding nitriles in fair to good yields. NiBr2–PPh3 can be used in place of NiBr2(PPh3)2 if MCN is added after reduction. In addition, less reactive halides, such as o-dichlorobenzene and o-chlorobenzonitrile, were fairly smoothly cyanated by the use of NiBr2–1,1′-bis(diphenylphosphino)ferrocene.

The cyanation of chlorobenzene catalyzed by [Ni(PPh3)n], which was generated in situ from [NiBr2(PPh3)2]–Zn–PPh3 (Ni:Zn:P = 1:3:2 molar ratio), was carried out at 60 °C using KCN or NaCN in hexamethyl phosphoric triamide (HMPA). Kinetic analyses revealed that the reaction rates in the KCN–HMPA system were zero order for both of chlorobenzene and nickel concentrations, and two-thirds order for KCN. The determination of the kinetic order for NaCN was difficult due to its high solubility in HMPA since excess cyanide ion inhibited the reaction. Zinc bromide which was formed with [Ni(PPh3)n] from [NiBr2(PPh3)2]–Zn–PPh3, acted as an important cocatalyst for the successful cyanation by comparison with [Ni(cod)2] (cod = 1,5-cyclooctadiene)–PPh3 system. Based on these experimental results, a reaction mechanism was proposed and discussed.

The cyanation of 3-bromopyridine catalyzed by in situ generated Ni(PPh3)n was examined with various MCN (M = K, Na)-dipolar aprotic solvent systems by four procedures. Under certain reaction conditions, 3-bromopyridine and several heteroaromatic halides were cyanated to give the corresponding nitriles in fair to good yields. Noticeable differences in reactivity among 3-bromopyridine, 3-bromofuran, 3-bromothiophene, and bromobenzene were observed.

Aryl mesylates were found to be deoxygenatively reduced into the corresponding aromatic hydrocarbons by using nickel(0)-dppb/PPh3 catalyst with zinc powder and an alcohol as a hydrogen donor.

The thermal reaction of citraconic acid (2) in water gives a mixture of products similar to that obtained from itaconic acid (1) in water. After 22 h at 170 °C, the equilibrium composition about 74%, 18%, and 8% 1, 2, and mesaconic acid respectively. At the optimum conditions (170 °C for 3 h), the yield of 1 is 65%. The mechanism of the reaction is discussed.