The activity of HBF4 (aqueous solution) as a catalyst in propargylation reactions is presented. Diverse types of nucleophiles were employed in order to form new C–O, C–N and C–C bonds in technical acetone and in air. Good to excellent yields and good chemoselectivities were obtained using low acid loading (typically 1 mol-%) under simple reaction conditions.
The asymmetric vinylogous Mannich reaction (AVMR) of α,α‐dicyanoalkenes with α‐fluoroalkyl sulfinyl imines has been successfully accomplished. This transformation is unprecedented with fluorinated imines and, at the same time, the use of dicyanoalkenes in AVMR has been scarcely reported. Several fluorinated sulfinyl imines are compatible with the process, which gives access to a family of chiral fluorinated amines with an excellent level of stereocontrol. Interestingly, the selectivity found in our protocol is the opposite of that encountered in analogous, previously reported AVMRs. Additionally, the synthetic applicability of the addition products has been exemplified with several transformations showing the particular reactivity of the dicyanoalkene moiety of these α‐fluorinated amines.magnified image
The total synthesis of (+)-anaferine and (−)-dihydrocuscohygrine is described. Bidirectional cross metathesis/double intramolecular aza-Michael reactions were the key steps.
A novel strategy for the synthesis of policyclic trifluoromethyl arenes has been devised. It involves a DBU-promoted tandem cycloaromatization reaction of dicyanoalkenes and fluorinated conjugated sulfinyl imines. This unprecedented transformation...
An efficient synthesis of tryptamines
is developed. Indole structures
were constructed using 2-iodoaryl allenyl amines as electron acceptors
and radical cyclization precursors. Radical–radical coupling
of indolyl methyl radicals and azaallyl radicals led to the tryptamine
derivatives. The utility and versatility of this method are showcased
by the synthesis of 22 examples of tryptamines in ≤88% yield.
In each case, indole formation is accompanied by in situ removal of
the Boc protecting group.
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