Page 955 - Advanced Organic Chemistry Part B - Reactions & Synthesis

CH 2 TESO 931
OTES
CO CH 3
2
CH 2 SECTION 10.2
several CH 2
Reactions Involving
PMBO steps
PMBO PMBO Carbenes and Related
TBDMSO Intermediates
TBDMSO TBDMSO
10.2.3.5. Enantioselective Cyclopropanation. Enantioselective versions of both
copper and rhodium cyclopropanation catalysts are available. The copper-imine class
of catalysts is enantioselective when chiral imines are used. Some of the chiral ligands
that have been utilized in conjunction with copper salts are shown in Scheme 10.10.
Several chiral ligands have been developed for use with the rhodium catalysts,
among them are pyrrolidinones and imidazolidinones. 207 For example, the lactamate
of pyroglutamic acid gives enantioselective cyclopropanation reactions.

Scheme 10.10. Chiral Copper Catalysts Used in Enantioselective Cyclopropanation

1 a CH 3 CH 3 2 b O O 3 c O O
O O Ph
Ph N N N N
N N
Ph Ph (CH ) C Cu(II) C(CH 3 3
)
3 3
R
R CuClO (CH CN) 4 10-2 10-3
3
4
SCF 10-1
CuO 3 3
R = C H , C(CH )
2 5
3 3
CH 3
4 d 5 e CH 3 CH 3
O N O 6 f
CH Ph OC H
2
4 9
N N N
R O – – ( ) 2
R O O O
10-4
Cu(I) complex N N C(CH )
3 3
Cu(II)
R = CH OSiC(CH ) C(CH ) ; C(CH 3 ) 3 C(CH )
3 3
3 2
2
) OSi(CH )
C(CH 3 2 3 3 3 3 10-5 10-6
Cu(I) complex
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