Page 784 - Advanced Organic Chemistry Part B - Reactions & Synthesis

760 CH 3
CH CH CH O
CH CH 2 [Rh(acac)(CO) 2 ] 2 2
CHAPTER 8 CH O
H SO Na)
P(C 6 5 3 3 +
Reactions Involving
Transition Metals 2,6-dimethyl-β-cyclodextrin
100% yield,
3.2:1 ratio
Ref. 283
The key steps in the reaction are addition of hydridorhodium to the double bond
of the alkene and migration of the alkyl group to the complexed carbon monoxide.
Hydrogenolysis then leads to the aldehyde.

O O
H 2
+ HRh(CO) Rh C O + Rh C Rh H + HC

Carbonylation can also be carried out under conditions in which the acylrhodium
intermediate is trapped by internal nucleophiles.

, CH 3
Rh(OAc) 2
PPh +
CH CHCH CH CH 2 3 N O O
3
2
CO, H , CH 3 CH N
NH 2 2 H 3 80% yield,
H OH
C 2 5 H Ref. 284
70:30 ratio
The steps in the hydroformylation reaction are closely related to those that occur
in the Fischer-Tropsch process, which is the reductive conversion of carbon monoxide
to alkanes and occurs by a repetitive series of carbonylation, migration, and reduction
steps that can build up a hydrocarbon chain.
+H 2 +CO
+
M CO M CO M CH 3 OC M CH 3
O
+H 2
OC M CH 3 M C CH 3 M CH CH 3
2
O
CO +H
2
M CH CH 3 M C CH CH 3 M CH CH CH 3 etc.
2
2
2
2
The Fischer-Tropsch process is of considerable economic interest because it is the
basis of conversion of carbon monoxide to synthetic hydrocarbon fuels, and extensive
work has been done on optimization of catalyst systems.
The carbonylation step that is involved in both hydroformylation and the Fischer-
Tropsch reaction can be reversible. Under appropriate conditions, rhodium catalyst can
be used for the decarbonylation of aldehydes 285 and acyl chlorides. 286
O O
RCH + Rh(PPh ) Cl RH RCCl + Rh(PPh ) Cl RCl
3 3
3 3
283
E. Monflier, S. Tilloy, G. Fremy, Y. Castanet, and A. Mortreux, Tetrahedron Lett., 36, 9481 (1995).
284 D. Anastasiou and W. R. Jackson, Tetrahedron Lett., 31, 4795 (1990).
285 J. A. Kampmeier, S. H. Harris, and D. K. Wedgaertner, J. Org. Chem., 45, 315 (1980); J. M. O’Connor
and J. Ma, J. Org. Chem., 57, 5074 (1992).
286
J. K. Stille and M. T. Regan, J. Am. Chem. Soc., 96, 1508 (1974); J. K. Stille and R. W. Fries, J. Am.
Chem. Soc., 96, 1514 (1974).