Copper-catalyzed tandem phosphorylative allenylation/cyclization of 1-(o-aminophenyl)prop-2-ynols with the P(O)–H species: access to C2-phosphorylmethylindoles

Abstract

A novel method to synthesize C2-phosphorylmethylindoles via the carbocation formation initiated tandem phosphorylative allenylation/cyclization of 1-(o-aminophenyl)prop-2-ynols with the P(O)–H species has been developed.

Recent Advances in the Synthesis of Heterocyclics via Cascade Cyclization of Propargylic Alcohols

“…Lately, Chen and co‐workers described an efficient copper‐catalyzed cascade phosphorylative allenylation/cyclization of 1‐( o ‐aminophenyl)prop‐2‐ynols 149 with disubstituted phosphine oxides, providing C2‐phosphorylmethlindoles 151 in moderate to good yields (Scheme 60). [81] Moreover, this approach could be also extended to 1‐( o ‐hydroxyphenyl)prop‐2‐ynols, generating the corresponding phosphorylated benzofurans in moderate yields under standard conditions. Control experiments results demonstrated that the allenylphosphoryl intermediate A involved to form the desired product 151 through a 5‐ exo ‐trig pathway.…”

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

“…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. Furthermore, Chen and co‐workers reported a copper‐mediated cascade reaction of propargylic alcohols with diarylphosphine oxides as the nucleophilic species [11g] . As a continuation of our efforts in developing copper‐ and silver‐mediated transformations in isocyanide chemistry, [12] herein we report a copper‐catalyzed heteroaromatization of propargylic alcohols with p‐toluenesulfonylmethyl isocyanide (TosMIC), providing access to diverse sulfonyl benzofurans and indoles (Figure 1).…”

Relay Cu(I)/Brønsted Base Catalysis for Phospha‐Michael Addition/5‐exo‐dig Cyclization/Isomerization of in situ Formed aza‐Alkynyl o‐quinone methides with P(O)−H compounds to C3‐Phosphorylated Indoles

“…Hydroamination triggered reactions have been well documented in which A undergoes 5‐ exo ‐ dig or 6‐ endo ‐ dig cyclization to form indoles [1] or quinolines [2] (Scheme 1a). However, reactions that proceed through prior dehydration to generate carbocation [5a] or aza ‐alkynyl o ‐quinone methides ( N ‐ o ‐AQMs) [5b–c] are much less common. Very recently, our group have reported the first example of carbocation formation initiated tandem phosphorylative allenylation/5‐ exo ‐ dig cyclization of 1‐( o ‐aminophenyl)prop‐2‐ynols to afford C2‐phosphorylmethylindoles (Scheme 1b) [5a] …”