A palladium(II) catalyst,
in the presence of Selectfluor, enables
the efficient and chemoselective transformation of primary amides
into nitriles. The amides can be attached to aromatic rings, heteroaromatic
rings, or aliphatic side chains, and the reactions tolerate steric
bulk and electronic modification. Dehydration of a peptaibol containing
three glutamine groups afforded structure–activity relationships
for each glutamine residue. Thus, this dehydration can act similarly
to an alanine scan for glutamines via synthetic mutation.
Phenylcyanocarbene was generated by the reaction of azide with a hypervalent iodonium alkynyl triflate and reacted in situ with 21 different carbocyclic and heterocyclic aromatic compounds. These reactions led to more complex products that frequently underwent subsequent rearrangements. The reactivity was further explored in a mechanistic study to ascertain the chemoselectivity and stereospecificity.
We
herein report the development of a protocol for the olefination
of oximes, resulting in cyclic alkene products. Our approach relies
on the in situ formation of Ru alkylidenes from [RuCl2(p-cymene)]2 and 3,3-diphenylcyclopropene as carbene
precursors and gives rise to the desired functionalized alkenes in
yields up to 58%. Compared to our previously reported strategy for
oxime olefination, it foregoes the use of commercially available Ru
alkylidenes, including Hoveyda–Grubbs 2. This is desirable
concerning the overall costs of this transformation and also provides
important mechanistic insights into the development of future catalytic
variants of this reaction as the alkylidenes required for efficient
olefination can be generated in situ.
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