Copper‐Catalyzed Dehydrative Cyclization of 1‐(2‐Hydroxyphenyl)propargyl Alcohols with P(O)H Compounds for the Synthesis of 2‐Phosphorylmethylbenzofurans

Abstract

A tetrakis(acetonitrile)copper(I) hexafluorophosphate [Cu(MeCN)PF6]‐catalyzed dehydrative reaction of 1‐(2‐hydroxyphenyl)propargyl alcohols with diarylphosphine oxides has been developed to provide an efficient synthesis of phosphorylated benzofurans in good to high yields. In the presence of a catalytic amount of an organic base, a variety of H‐phosphonates and H‐phosphinates can also be employed as good substrates to produce the corresponding products in moderate yields. The reaction has significant economical and ecological advantages since the formation of a new C(sp3)–P bond and the benzofuran framework could both be achieved using an inexpensive copper catalyst with water produced as the sole by‐product. Some synthetic transformations of the product have also been demonstrated.magnified image

The Copper-Catalyzed Reaction of 2-(1-Hydroxyprop-2-yn-1-yl)phenols with Sulfonyl Azides Leading to C3-Unsubstituted N-Sulfonyl-2-iminocoumarins

“…The 2-(1-hydroxyprop-2-yn-1-yl)­phenols and sulfonyl azides employed in this work were all known compounds and prepared by established and conventional procedures. So, in the case of the former substrates, this involved the addition of ethynylmagnesium bromide to the relevant o -hydroxybenzaldehyde or to o -hydroxyacetophenone and, in the latter case, reaction of the appropriate sulfonyl chloride with sodium azide in aqueous acetone …”

Copper in Efficient Synthesis of Aromatic Heterocycles with Single Heteroatom

“…Shen and co-workers achieved the synthesis of phosphorylated benzo[b]furans (130) by copper-catalyzed dehydrative reaction (Scheme 43) between 1-(2hydroxyphenyl)propargyl alcohols (128) and P(O)H compounds (129). [65] Scheme 43. Synthesis of phosphorylated benzo[b]furans.…”

Synthesis of Sulfonylated Heterocycles via Copper‐Catalyzed Heteroaromatization/Sulfonyl Transfer of Propargylic Alcohols

“…In this regard, copper has proven to be a prominent metal for these transformations [11] . For instance, tandem protocols proceeding through copper‐assisted cyclization and dehydrative cross‐coupling to generate benzoheteroles have been disclosed [11a–d] . Recently, Zhu [11e] and Du [11f] independently developed copper‐catalyzed reactions of propargylic alcohols with a nucleophile via alkynyl ortho‐quinone methide (o‐QM) intermediates.…”