Abstract
A preparatively straightforward methodology has been developed which allows the assembly
of silicon-containing carbocycles as mixtures of diastereomers with silicon as the
sole center of stereogenic information. One-step construction of the chiral cyclic
silanes is realized by reaction of equimolar amounts of a dibromide and a chirally
modified dichlorosilane under Barbier conditions giving access to several monofunctionalized
1-sila-1,2,3,4-tetrahydronaphthalenes and a corresponding phenanthrene derivative.
Facile large scale syntheses of 3-(2-bromoaryl)propyl bromides as well as dichlorosilanes
have been elaborated. This highly convergent methodology relies on the novel (-)-menthyl-oxy-substituted
dichlorosilanes, which have the chiral auxiliary for the subsequent optical resolution
installed. These enantiopure dichlorosilanes are useful building blocks for a general
and modular one-step approach to silanes with silicon-centered chirality since this
strategy avoids the linear sequences reported in literature. The optical resolution
has been exemplarily optimized for the 1-phenyl-1-sila-1,2,3,4-tetrahydronaphthalene
derivative and the absolute configuration has been established by X-ray crystallography.
The chiral auxiliary is stereospecifically displaced by simple reduction providing
the highly enantioenriched silane (er = 98:2) which is enantiospecifically chlorinated
as verified by a Walden inversion at silicon.
Key words
Grignard reactions - cyclizations - enantiomeric resolution - heterocycles - silicon
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