Page 560 - Advanced Organic Chemistry Part B - Reactions & Synthesis

534 Scheme 6.6. (Continued)

CHAPTER 6 j CH 2 CH 2 CH 3
10 heat
+
Concerted CH 3 CO 2 (CH 2 ) 3 CH NCH(CH 2 ) 2 CH CH 2 CH 3 CH 2 CH 2 N
Cycloadditions, CH 3 CO 2 O
Unimolecular O –
Rearrangements, and
Thermal Eliminations
11 k CH 3 OC(CH 3 ) 3 CH 3 OC(CH 3 ) 3
NaOCl
CH 3 O 2 C CH 3 O 2 C
CH 3
CH 3
(CH 2 ) 2 CH NOH O
N 96%
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Entry 7 is another intramolecular nitrone cycloaddition, but in this case the hydroxyl-
amine function is present in the alkene.

PhSO (CH )
PhSO (CH ) H 2 2 3
2 3
2
H
N + CH N
CH 3 3 O
– O (CH ) CH 3 (CH ) CH 3
2 2
2 2
The product of the reaction in Entry 8 was used in the synthesis of the alkaloid
pseudotropine. The proper stereochemical orientation of the hydroxy group is deter-
mined by the structure of the oxazoline ring formed in the cycloaddition. Entry 9
portrays the early stages of synthesis of the biologically important molecule biotin.
The reaction in Entry 10 was used to establish the carbocyclic skeleton and stereo-
chemistry of a group of toxic indolizidine alkaloids found in dart poisons from frogs.
Entry 11 involves generation of a nitrile oxide. Three other stereoisomers are possible.
The observed isomer corresponds to approach from the less hindered convex face of
the molecule.

CH 3
N+ –
O
CH 3 O 2 C OC(CH 3 ) 3
CH 3