ca01 only detailed ToC 1..24

1.1.4 Nickel–Alkene Complexes 75
4-Methoxyphenol (96,R 1 = 4-MeOC 6H 4); Typical Procedure: [172]
A 1.5 M soln of DIBAL-H in toluene (600 ìL, 0.9 mmol) was added dropwise to a stirred soln
of 95 (R 1 = 4-MeOC 6H 4; 100 mg, 0.6 mmol) and NiCl 2(dppp) (3 mg, 6 ìmol) in Et 2O(2mL)
under argon at 0 8C. The mixture was stirred for 5 min at the same temperature and then
for 2 h at rt. The mixture was diluted with Et 2O (3 mL), quenched by addition of H 2O
(600 ìL) and, after stirring for 1 h, dried (MgSO 4), filtered through a Celite pad, and concentrated
under reduced pressure to leave the crude product which was chromatographed
(silica gel, 3 g, Et 2O/hexane 1:4) to give pure 96 (R 1 = 4-MeOC 6H 4); yield: 68mg
(90%).
1.1.4.8 Method 8:
Alkene Hydrozincation
The nickel-catalyzed hydrozincation of alkenes provides a novel method for the preparation
of functionalized organozincs such as (97) (Scheme 77). [174,175] The resulting functionalized
organozincs may be transformed into cuprate reagents and then alkylated with a
variety of electrophiles. A hydronickelation step is likely involved in the reaction pathway.
Scheme 77 Nickel-Catalyzed Hydrozincation of Alkenes [174,175]
2
R 1
ZnEt 2
+ ZnEt 2
Ni(acac) 2 1
R 1
Dioctylzinc [97,R 1 =(CH 2) 5Me]: [175]
2
1−2 mol% Ni(acac)2 1
1−4 mol% cod
acac
LnNi Et
Zn
R 1 = (CH 2) 5Me 38%
ZnEt 2
acac
LnNi
H
acac
LnNi Zn
1 R +
2
97
R 1
R 1
acac
LnNi H
2 H 2C CH 2
H2C CH2
CAUTION: Large quantities of gaseous ethene are produced in the reaction, especially for largescale
reactions!
A 50-mL two-necked flask equipped with an argon inlet, a magnetic stirring bar, and a septum
cap was charged with [Ni(acac) 2](1; 26 mg, 0.10 mmol, 1 mol%) and cycloocta-1,5-diene
(22 mg, 0.20 mmol, 2 mol%), followed by oct-1-ene (1.12 g, 10.0 mmol). The mixture
was cooled to 0 8C, and ZnEt 2 (0.61 mL, 6.0 mmol, 0.6 equiv) was added dropwise. The cooling
bath was removed, and the mixture was stirred in a preheated oil bath at 50–60 8C for
3 h. The conversion was checked by iodolysis of an aliquot of the mixture (40–45%). The
excess ZnEt 2 and unreacted alkene was distilled off in vacuo, yielding 97 [R 1 =(CH 2) 5Me];
yield: 0.65 g (38%).
R 1
for references see p 79