ca01 only detailed ToC 1..24

60 Science of Synthesis 1.1 Organometallic Complexes of Nickel
Nickel-Catalyzed [2 +2+2] Cycloadditions; General Procedure: [103]
A 0.02–0.04 M soln of Ph 3P (0.4–1.0 equiv) in THF was added to [Ni(cod) 2](2; 0.20–0.25 equiv)
at 0 8C and stirred for 2 min. The nickel soln was transferred by cannula to a 0.4–0.5 M soln
of the simple enone (5.0 equiv) and the alkynyl enone substrate (1.0 equiv) in THF at 0 8C.
The reaction was stirred at 0 8C for 5 min and then at 258C until the starting material was
consumed (generally 1.5–3.0 h). The mixture was subjected to an extractive workup with
NH 4Cl/NH 4OH (pH 8) buffer and Et 2O followed by flash chromatography (silica gel).
1.1.3.8 Method 8:
Alkyne Carbonylation
The carbonylation of alkynes in the presence of methanol or water and carbon monoxide
produces Æ,â-unsaturated carboxylic acids or esters (Scheme 50). [7,104] This reaction is rarely
used in large-molecule synthetic applications; however, it has been very important in
the industrial preparation of acrylic acid from acetylene.
Scheme 50 Preparation of Acrylic Acid From Acetylene [104]
H H + H 2O + CO
1.1.3.9 Method 9:
Alkyne Hydrocyanation
The hydrocyanation of alkynes provides a direct method for preparing Æ,â-unsaturated
nitriles such as 67. The reactions proceed at 1208C in an autoclave with hydrogen cyanide
and catalytic tetrakis(triphenyl phosphite)nickel(0) (Scheme 51). [105] Lower temperatures
may be employed if the alkyne and hydrogen cyanide are added very slowly. The hydrocyanation
of dienes and alkenes (Sections 1.1.1.6 and 1.1.4.5) are much more widely used
procedures than the hydrocyanation of alkynes.
Scheme 51 Hydrocyanation of Alkynes [105]
Ph Ph + HCN
(E)-2,3-Diphenylprop-2-enenitrile (67): [105]
Ni
Ni[P(OPh) 3] 4
93%
Ph
H
H
H
H
Ph
CN
67
CAUTION: Hydrogen cyanide is highly toxic! Appropriate safety precautions and procedures
should be adopted during all stages of the handling and disposal of this reagent.
Into a 75-mL stainless steel autoclave were placed Ni[P(OPh) 3] 4 (0.24 g, 0.2 mmol), P(OPh) 3
(0.8g, 2.5 mmol), PhC”CPh (7 g, 39 mmol), HCN (1.25 mL, 32 mmol), and benzene (25 mL).
The vessel was heated at 1208C for 18h. After cooling, the benzene was removed by distillation.
Column chromatography (basic alumina, activity II, Et 2O/petroleum ether 1:9)
followed by distillation gave the unsaturated nitrile 67; yield: 6.12 g (93%).
1.1.3.10 Method 10:
Alkyne Hydrosilylation
Two distinct product classes, silylethenes and 1,2-disilylethenes, may be obtained from
the hydrosilylation of alkynes. The addition of trichlorosilane to alkynes in the presence
CO2H