Tandem Hydroformylation/Acyloin Reaction - The Synergy of Metal Catalysis and Organocatalysis Yielding Acyloins Directly from Olefins
作者:Karoline A. Ostrowski、Thiemo A. Faßbach、Andreas J. Vorholt
DOI:10.1002/adsc.201401031
日期:2015.5.4
A novel, atom efficient, orthogonal tandem catalysis was developed yielding acyloin products (α‐hydroxy ketones) directly from olefins under hydroformylation conditions. The combination of a metal‐catalysed hydroformylation and an organocatalysed acyloin reaction provides three atom efficient CC bond formations to linear, multifunctional molecules via linkage of the intermediate n‐aldehydes. Additionally
Decreasing Side Products and Increasing Selectivity in the Tandem Hydroformylation/Acyloin Reaction
作者:Karoline A. Ostrowski、Thiemo A. Faßbach、Dennis Vogelsang、Andreas J. Vorholt
DOI:10.1002/cctc.201500727
日期:2015.9.1
to a variety of olefins is enabled with comparable excellent selectivities up to >99 % for the first and second reaction step, therefore a general synthesis for the conversion of olefins into acyloins is found. Furthermore, very good to excellent yields for the intermediates and final acyloin products were observed within two catalysed reactions in one preparative step. The acyloin product was applied
Several methods for the preparation of long-chain vicinal diketones are examined. The acyloincondensation, followed by oxidation, provides an excellent route to symmetrical compounds but is not satisfactory for unsymmetrical diketones. The latter are prepared (i) from dialkylacetylenes by semihydrogenation, hydroxylation, and oxidation with aqueous N-bromosuccinimide; and (ii) from an α-acetoxy-acid
Benzoins 4 (2-hydroxyethanones substituted with aryl groups at the 1- and 2-positions) were prepared by self-condensation of aromatic aldehydes 3 using catalytic amounts of azolium salts 1 and 2 in excellent yields.1, 3-Dimethylbenzimidazolium iodide (2) was an effective catalyst for the preparation of acyloins 6 (2-hydroxyethanones substituted with alkyl groups at the 1- and 2-positions) by self-condensation of aliphatic aldehydes 5. On the other hand, an attempt at the condensation of hexanal (5d) catalyzed by 1, 3-dimethylimidazolium iodide (1) failed to yield the acyloin 6d, and instead the aldol-type condensed product 8d was obtained.