Carbanions pentalene

This type of asymmetric conjugate addition of allylic sulfinyl carbanions to cyclopen-tenones has been applied successfully to total synthesis of some natural products. For example, enantiomerically pure (+ )-hirsutene (29) is prepared (via 28) using as a key step conjugate addition of an allylic sulfinyl carbanion to 2-methyl-2-cyclopentenone (equation 28)65, and (+ )-pentalene (31) is prepared using as a key step kinetically controlled conjugate addition of racemic crotyl sulfinyl carbanion to enantiomerically pure cyclopentenone 30 (equation 29) this kinetic resolution of the crotyl sulfoxide is followed by several chemical transformations leading to (+ )-pentalene (31)68. 

A new synthesis of pentalenic acid (273) with virtually complete stereo- and regio-control uses Michael addition of the carbanion of the allylic phosphonate (272).Phosphonate-based olefination of suitably substituted cinnamaldehydes has been used to prepare a number of (E,E)-l,4-diarylbuta-1,3-dienes (274) with properties suitable for use in liquid crystal display devices. 139 The meso-form (276) of a tetrahydrotetrabenzocyclododecene has been synthesized by bis-alkylation of the bis-ylide (275) (276) isomerizes to the racemic form on heating. 1 11... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ , ]

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