| Summary: | With the use of lithium (trimethylstannyl)(cyano)cuprate (123), α, β -acetylenic esters of
general structure 100 were converted into the corresponding alkyl (E)- and (Z)-3-
trimethylstannyl-2-alkenoates 89 and 91. Homoallylic diiodides of general structures 98 and
99 were synthesized, via a sequence of transformations, from the corresponding esters 89
and 91, respectively. Deconjugation-alkylation of ailcyl (E)- and (Z)-3-trimethylstannyl-2-
ailcenoates 89 and 91 with electrophiles 96 and 97, provided, stereoselectively, the
functionalized esters of general structure 206.
Palladium(0)-catalyzed intramolecular cross-coupling reaction of esters 206 provided
alkyl 2,3-bis(alkylidene)cyclopentanecarboxylates of general structure 219 in good yields
and in a stereochemically defmed fashion. Thus, a general strategy for the preparation of
alkyl 2,3-bis (alkylidene)cyclpentanecarboxylates possessing E,E-, E,Z- and Z,Z
configurations (i.e. 81,82 and 84) was established. The limitations of this palladiumcatalyzed
intramolecular coupling reaction were shown by the inability to provide the Z,E
diene 230 in a stereocontrolled manner, and by the low yield obtained in the preparation of
229.
The dihedral angles between the two exocycic C=C bonds in the (Z,Z)-diene system of
general structure 84 were determined by X-ray crystallographic analysis of crystalline
derivatives of alkyl (Z,Z)-2,3-bis(alkylidene)cyclopentanecarboxylates 222, 228 and 229.
The magnitude of the dihedral angles in compounds 237,238,241, 243 and 247 ranges
from 48.6° to 58.00.
A new CuCl-mediated intramolecular coupling reaction of vinyl halide and
vinyltrimethylstannane functions was discovered in conjunction with studies directed toward
the synthesis of the Z,E-diene 230 in a stereochemically defined manner and toward the
optimization of the yield in the preparation of 229. This method has been applied
successfully to the preparation of a number of alkyl 2,3-bis(alkylidene)cyclopentanecarboxylates
possessing E,E-, E,Z-, Z,E- and Z,Z-configurations (81,82,83 and 84) and
to the synthesis of a variety of bicydic compounds containing a conjugated diene system
(253,289-293). A provisional mechanism was proposed for this new coupling procedure.
The Diels-Alder reactions of the dienophiles TCNE and MVK with the alkyl 2,3-
bis(alkylidene)cyclopentanecarboxylates of general slructure 219 as well as the related dienes
of general structure 314 were investigated. It was found that these Diels-Alder reactions
occur with high face-, endo/exo- and regioselectivities.
[chemical compound diagrams] === Science, Faculty of === Chemistry, Department of === Graduate
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