Cyclic ring-expansion approach

Further details of the ring expansion of 1-vinylcyclopropanals and (l-hydroxy-cyclopropyl)methanols to cyclobutanols have appeared. A useful approach to cyclobutanone annelation is the addition of the readily available a-methoxyvinyl-lithium to a cyclic ketone, followed by Simmons-Smith reaction and hydrolytic rearrangement (Scheme 11) ... 

Kudo, H., Sato, M., Wakai, R. et al (2008) A novel approach to cyclic polysulfides via the controlled ring-expansion polymerization of cyclic thiourethane with thiiranes. Macromolecules, 41,521-523. 

Cyclic macromolecules, or ring polymers, have been synthesized by one of three fundamental approaches (1) backbiting of linear precursors (Jones etal, 1974 Wright and Beevers, 1986 Ruddick et al, 1999 Kricheldorf, 2003 Boston and Beckham, 2010a), (2) ring expansion by bond insertion (Bielawski et al, 2002 Shea et al, 1998 Kricheldorf et al, 1998 Kricheldorf et al, 2002 Bielawski et al, 2003), or (3) end-to-end coupling of difunctional linear precursors in dilute solution (Geiser and Hocker, 1980 Roovers and Toporowski, 1983 ... 

Olefins may be converted in high yield to a-ahtoroketones by treatment with chromyl chloride in acetone. a-Carboxyketones, generally relatively inaccessible, can be prepared by treatment of ketones with lithium 4-methyl-2,6-di-tert-butylphenoxide and carbon dioxide. Cyclic ketones result from ring expansion of methylene cycloalkanes with cyanogen azide followed by hydrolysis, a procedure which complements the standard diazo-methane-ketone approach. Functionalized cis-bicyclic ketones can be synthesized by haloketal cyclizatlon followed by hydrolysis. ... 

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