Zirconocene catalyzed diastereoselective carbometalation of cyclobutenes

Abstract

We functionalize cyclobutene species into polysubstituted metalated cyclobutanes through the Dzhemilev reaction.

A catalytic asymmetric cross-coupling approach to the synthesis of cyclobutanes

“…Carbometallation processes are among the most fundamental processes in asymmetric catalysis and are often triggered by the release of ring strain, but such a process is previously unknown for unactivated cyclobutenes. While copper-catalysed asymmetric hydroboration and hydroamination are known to add heteroatom nucleophiles to cyclobutenes 17,18 , the asymmetric addition of carbonnucleophiles via carbometallation to form new carbon-carbon bonds remains elusive 19 . Even nonenantioselective carbometallation approaches for four-membered rings are non-trivial and rare 19 , and strategies that work very well for more strained species like cyclopropenes do not generally translate to cyclobutenes 20 .…”

Consecutive and Selective Double Methylene Insertion of Lithium Carbenoids to Isothiocyanates: A Direct Assembly of Four‐Membered Sulfur‐Containing Cycles

“…Conceptually, these precedents could be ascribed to the well-established carbonyl-oxirane (and related imine-aziridine) homologative chemistry: [13] this is, the cyclic cluster is constructed via the incorporation of a single C1 unit delivered by the carbenoid donor. [14] We wondered if homologation tactics with C1 carbenoids could promote the assembly of four-membered cycles [15] through the consecutive release of two methylene fragments on a proper electrophile. Crucial for the successful reaction design was ensuring that the homologation sequence could reach completion within the short lifetime of the carbenoid used.…”

p-Anisaldehyde-Photosensitized Sulfonylcyanation of Chiral Cyclobutenes: Enantioselective Access to Cyclic and Acyclic Systems Bearing All-Carbon Quaternary Stereocenters

“… Cyclopropanes and cyclobutanes can be constructed in many ways, including through addition onto their unsaturated analogues and highly strained cyclopropenes and cyclobutenes . Cyclopropenes thus show a high reactivity toward addition of organometallic species − but, as expected, the extension of the strategy to cyclobutenes proved more difficult as illustrated by recent studies . A similar trend is observed in free-radical additions, where the reactivity of cyclobutenes was shown to be on the same order as that of cyclohexene and lower than that of cyclopropenes.…”

“…4 Cyclopropenes thus show a high reactivity toward addition of organometallic species 4a−d but, as expected, the extension of the strategy to cyclobutenes proved more difficult as illustrated by recent studies. 5 A similar trend is observed in free-radical additions, where the reactivity of cyclobutenes was shown to be on the same order as that of cyclohexene 6 and lower than that of cyclopropenes. Radical additions to cyclopropenes 6,7 and cyclobutenes 8 are thus rare.…”