Seven-and Eight-Membered Carbocycles

Gerard Buono, Herve Clavier, Laurent Giordano, AND Alphonse Tenaglia 

Aix Marseille Universite, Centrale Marseille, CNRS, Marseille, France 

Alternate strategies involving fragmentations or ring expansions that overcome the ring strains have also been proposed. To circumvent these constraints, transition-metal processes (catalytic or stoichiometric), which reorganize the transition state for 

Stereoselective Multiple Bond-Forming Transformations in Organic Synthesis, First Edition. Edited by Jean Rodriguez and Damien Bonne. 

Grubbs catalyst afforded tricyclic [7.5.6] and [7.6.6] ring systems as single diastere-omers in moderate to good yields. Since no specific structural feature in the substrates was found responsible for the observed diastereoselectivity, the authors assumed the RRM process occurs under kinetic control. 

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The Cope rearrangement is of great importance as a synthetic method e.g. for the construction of seven- and eight-membered carbocycles from 1,2-divinylcyclopropanes and 1,2-divinylcyclobutanes respectively (e.g. 11 12),... 

Metal TT-Complexes Formed by Seven- and Eight-Membered Carbocyclic Compounds, 4,353... 

Narasaka s chiral titanium catalyst, prepared from (Pr 0)2TiCl2 and a tartrate-derived (2R,3R)-l,l,4,4-tetraphenyl-2,3-0-(l-phenylethylidene)-l,2,3,4-butanetetrol, is utilized for the asymmetric [2+2] cycloaddition of A-acyl oxazolidinones to 1,2-propadienyl sulfides possessing a-substituents, which afford methylenecyclobutane derivatives with high enantiomeric purity. These chiral adducts are readily transformed to seven- and eight-membered carbocycles with chiral side chains by the ring-cleavage reaction and subsequent cationic cyclization of the chiral cyclobutane derivative [68] (Eq. 8A.44). 

Vinylogous modes of this rearrangement are also possible. Complex systems can be attained by utilizing a built-in electrophile in an intramolecular ring expansion/alkylation, as shown in equation (35). This kind of cyclization is applicable to seven- and eight-membered carbocyclic ring synthesis and proceeds with approximately 12 1 stereoselectivity, which is due to the more stable, parallel conformation depicted in equation (35). ... 

Metal x-Complexes formed by Seven- and Eight-Membered Carbocyclic Compounds, 4, 353 Nitrogen Groups in Metal Carbonyl and Related Complexes, 10, 115 Nitrosyls, 7, 211... 

Scheme 6.44 Stereocontrolled formation of seven- and eight-membered carbocycles using a combination of Brook rearrangement-mediated [3+4] annulation and epoxysilane rearrangement.

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