Page 713 - Advanced Organic Chemistry Part B - Reactions & Synthesis

Scheme 8.2. (Continued) 689

CH SECTION 8.1
CH 3 O
11 k CH 3 3 C H Organocopper
2 5
CH 3 O C 2 5 O CH O CH Intermediates
H
O O CH 3 3 O CH 3
CH 3 3
O Me CuLi
2
BF , –78°C CH 3 H O
3
H O CH 3 O
CH 3 CH 3
CH 3 O CH CH 3 80%
CH 3 3
12 l O O
CH 3 CH 2 CHCu, LiI, CH 3
Bu P
3
CH CH
–78°C 2
O H CH OCH 3 O H CH OCH 3
2
2
O O 95%
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In Entry 3, the trans stereochemistry arises at the stage of the protonation of the
enolate. Entry 4 gives rise to a cis ring juncture, as does the corresponding carbocyclic
compound. 59 Models suggest that this is the result of a steric differentiation arising
from the axial hydrogens on the -face of the molecule.

CH 3 N O
H
H
H

Entries 5 to 9 illustrate some of the modified reagents and catalytic procedures.
Entry 5 uses a phosphine-stabilized reagent, whereas Entry 6 includes BF . Entry 7
3
involves use of TMS-Cl. Entries 8 and 9 involve cyanocuprates. In Entry 9, the furan
ring is closed by a Mukaiyama-aldol reaction subsequent to the conjugate addition
(Section 2.1.4).
59
S. M. McElvain and D. C. Remy, J. Am. Chem. Soc., 82, 3960 (1960).