2.05 Propargyl and Allenyl Organometallics

Catalytic, Enantioselective Synthesis of Allenyl Boronates

“…Allenyl boron reagents are a valuable class of carbon nucleophiles that are widely used in the propargylation/allenylation of carbonyl compounds. , Stereocontrol in such addition reactions has previously been achieved through use of chiral auxiliaries, chiral catalytic Lewis/Brønsted acids/bases, or chiral metal complexes, , including enantioselective variants. Enantioenriched, axially chiral allenyl boronates are an attractive class of coupling partners, as they are capable of serving as the sole source of stereoinduction in carbonyl addition reactions , or can be employed with a chiral promoter to achieve control of absolute and relative stereoinduction toward densely functionalized targets .…”

A Computational Investigation of the Ligand-Controlled Cu-Catalyzed Site-Selective Propargylation and Allenylation of Carbonyl Compounds

“…The addition of organometallic reagents to ketones and aldehydes is a highly useful synthetic method for the construction of carbon–carbon bonds. 1 The corresponding propargylation 2 and allenylation 3 reactions have attracted considerable attention, as the functionality in the resulting allenyl and propargyl carbinols is useful for further structural modification. 4 To meet demand, various methods for the direct allenylation of carbonyl compounds have been reported, including those based on B, 5 Al, 6 Si, 7 Cr, 8 Zn, 9 and other Lewis acids 10 with propargyl species.…”

Zinc Amide Catalyzed Regioselective Allenylation and Propargylation of Ketones with Allenyl Boronate

“…Allenylation and propargylation of ketones afford tertiary allenyl and homopropargyl alcohols. These compounds are common motifs in biologically active natural products as well as essential synthetic units, but they cannot be prepared by the reduction (hydrogenation) of carbonyl compounds. Therefore, the carbon–carbon bond formation with ketones is crucial; however, control of reactivity and selectivity is difficult due to the sterically hindered nature of ketones compared with aldehydes.…”