Enantiodivergent Synthesis of Allenes by Point‐to‐Axial Chirality Transfer

Abstract

General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Abstract: An enantiodivergent method for the synthesis of multiply substituted allenes is described. Highly enantioenriched,p oint-chiral boronic esters were synthesized by homologation of a-seleno alkenyl boronic esters with lithiated carbamates and eliminated to form axially chiral allene products.B ye mploying either oxidative or alkylative conditions,b oth syn and anti elimination could be achieved with complete stereospecificity.The process enables the synthesis of either Mo rPallenes from as ingle isomer of ap oint-chiral precursor and can be employed for the enantioselective assembly of di-, tri-, and tetrasubstituted allenes.

Synthesis of Allenes by 1,2-Elimination

“…Palladium catalyzed 1,2-elimination of vinyl boronic esters Aggarwal and co-workers have recently reported an enantiodivergent strategy for the synthesis of chiral allenes (Scheme 27). [58] In this work, α-seleno alkenyl boronic esters 109 underwent one-carbon homologation with lithiated carbamates to afford highly enantioenriched β-selenoboronic esters 110. These intermediates could be oxidized with m-CPBA to the corresponding selenoxides which underwent syn-elimination (see TS-syn), [59] forming allenes 111 with very high levels of enantiospecificity.…”

Transition‐Metal‐Catalyzed Synthesis of Chiral Allylboronates†

“…[ 1,41 ] Recently, Aggarwal and co‐workers successfully developed a lithiation‐borylation reaction, which can be applied for the stepwise and one‐pot homologation of chiral boronic esters with excellent stereospecificity. [ 42‐45 ]…”

Point-to-Axial Chirality Transmission: A Highly Sensitive Triaryl Chirality Probe for Stereochemical Assignments of Amines

“…The operation simplicity, on the one hand, and versatility of the sensors, on the other hand, make the imine-based probes particularly useful for chirality sensing. 63 , 64 , 66 Widely utilized in the asymmetric synthesis, i.e., allenes, point-to-axial chirality transfer 67 − 69 recently has gained popularity in chirality sensing. Now, point-to-axial chirality transfer is efficiently applied as the modus operandi of some chiroptical probes for the stereochemical characterization of optically active amines and other compounds.…”