ca01 only detailed ToC 1..24

2.6.2 Metal–Carbyne Complexes 103
Scheme 13 Carbonylmethylenation [60–62]
Ph
Ph
O
O
O
Ph
37
36
WOCl 3/MeLi (1:2) (1.5 equiv)
THF, −78 to 45 o C, 18 h
95%
Ph
O
1. A or B
2. H + OH OH OH
, H2O +
O
35
Ph
O
A: WOCl3/MeLi (1:2) (1 equiv) 43%
B: MoOCl3/MeLi (1:2) (1 equiv) 38%
MoOCl3/MeLi (1:2) (2 equiv)
THF, −78 to 20 oC, 18 h
Carbonylmethylenation of 4-(4-Acetylphenyl)-4-hydroxypentan-2-one (36);
Typical Procedure: [61]
To a red-brown suspension obtained by methylation of MoOCl 3(THF) 2 (1.57 g, 4.3 mmol)
with MeLi (8.7 mmol) in THF (30 mL) at –708C was added dropwise a soln of 4-(4-acetylphenyl)-4-hydroxypentan-2-one
(36; 0.48 g, 2.16 mmol) in THF (2 mL). The mixture was
further stirred at –708C for 4 h, followed by warming to rt over 12 h. This was hydrolyzed
with sat. aq NaHCO 3 (10 mL). After separation of the two phases and Et 2O extraction of the
aqueous phase, the combined organic fractions were dried (Na 2SO 4), and the solvent was
removed by rotary evaporation. Flash chromatography (3 cm ” 16 cm, silica gel, CH 2Cl 2/
acetone 40:1) afforded 2-(4-isopropenylphenyl)-4-methylpent-4-en-2-ol {fraction 1; yield:
0.04 g (9%); IR í~ max: 3500 cm –1 (br, OH); 1 H NMR (CDCl 3, ä): 4.77 [m, 1H, CH 2C(CHH)CH 3],
4.91 [m, 1H, CH 2C(CHH)CH 3], 5.09 [m, 1H, aryl-C(CHH)CH 3], 5.40 (m, 1H, aryl-
C(CHH)CH 3]} as a colorless oil, 2-(4-acetylphenyl)-4-methylpent-4-en-ol [fraction 2; yield:
0.18 g (38%); IR í~ max: 3420 cm –1 (br, OH); 1 H NMR (CDCl 3, ä): 4.75 (m, 1H, C=CHH), 4.91
(m, 1H, C=CHH)] as a yellow oil, and unreacted 4-(4-acetylphenyl)-4-hydroxypentan-2one
[fraction 3; yield: 0.08 g (17%)].
2.6.2 Product Subclass 2:
Metal–Carbyne Complexes
As for the case of carbene complexes, carbonyl-free carbyne (Schrock-type alkylidyne)
complexes are most common for high oxidation state (‡4) molybdenum and tungsten systems,
[63] although chromium examples are known. [64] For the purpose of formal oxidation
state assignment, the carbyne ligand is considered as (RC 3– ). The majority of d 0 complexes
possess the formula M(”CR)X 3, but many adducts with neutral two-electron donor ligands
L,M(”CR)X 3L n (n = 1 or 2), are also known. Derivatives with more electronegative X groups
(e.g., fluorinated alkoxides) form base adducts more readily. The most common supporting
ligands (X) are bulky alkyl ligands, alkoxides, and halides, but derivatives with
amides, and alkyl- and arylthiolates are also known. Typical ligands (L) are amines, ethers,
and phosphines. In lower formal oxidation states (+4 and +5), phosphines and halides or
cyclopentadienyl coligands are usually found. The halide derivatives are the most versa-
Ph
O
89%
+
Ph
5%
9%
2%
for references see p 135