Dioxa paracyclophane

The nomenclature of phanes is simple 32) It mainly defines the length(s) of the bridge(s) and their positions in the ring as illustrated by the following examples [6]para-cyclophane (2) 1,10-dioxa [10]paracyclophane (6), [2.2]paracyclophane (7), [2.2]meta-(8) and [2.2]metaparacyclophane (9) and [8](2,5)pyridinophane (70). The formulae show also the kind of projection used in this survey to illustrate stereochemical relations. 

An unambiguous correlation of the ansacompound dioxa[ll]paracyclophane-carboxylic acid (gentisic nonamethylene ether, 17) with cis-3-hydroxy-cyclohexane-... 

While for several phanes such as [njparacyclophanes, dioxa[n]para or [2.2]meta-paracyclophanes, the assignments by this rule were in agreement with the experimental results, they had to be revised for [2.2]meta- and [m][n]paracyclophanes after the application of more reliable methods. These discrepancies were discussed in previous sections (2.6.1, 2.9.1). A quadrant rule proposed for cyclic ketones includes also the configurational assignment to oxo[2.2]metacyclophanes (61-63) and stereoisomeric alcohols derived therefrom 113). 

The first example of catalytic and enantioselective orf/to-lithiation for the generation of planar chirality was recently reported [121], Enantioselective monolithiation and diUthiation of 1, -dioxa[n]paracyclophanes 19 are performed with i-BuLi in the presence of a catalytic or stoichiometric amount of sparteine. Quenching with various electrophiles provides access to chiral mono- and disubstituted paracyclophanes 20 and 21 with excellent ee s. 

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