Title Enantioselective , Stereodivergent Hydroazidation and Hydroamination of Allenes Catalyzed by Acyclic Diaminocarbene ( ADC ) Gold ( I ) Complexes Permalink

The gold-catalyzed enantioselective hydroazidation and hydroamination reactions of allenes are presented herein. ADC gold(I) catalysts derived from BINAM were critical for achieving high levels of enantioselectivity in both transformations. The sense of enantioinduction is reversed for the two different nucleophiles, allowing access to both enantiomers of the corresponding allylic amines using the same catalyst enantiomer. Allylic amines are an important functional motif in synthetic organic chemistry and they have been utilized in the synthesis of numerous biologically active compounds. Closely related allylic azides are valuable precursors for allylic amines, as well as for amino acids and amine-containing natural products. Allylic azides have typically been prepared via substitution reactions from the corresponding allylic halides, (homo)allylic alcohols, and their derivatives. More recently, Pdcatalyzed C¢H activation, and Au-catalyzed hydroazidation of allenes have been employed. While reports of the synthesis of allylic azides are numerous, methods for asymmetric azidation are few. Fewer still are enantioselective hydroazidation reactions, which have only been reported in a formal sense via conjugate addition to activated double bonds (Scheme 1). In light of recent examples of transition-metal catalysed asymmetric additions of nitrogen nucleophiles to allenes and the growing utility of organic azides, we sought to develop a gold(I)-catalyzed enantioselective hydroazidation of allenes. Cognizant of potential regioselectivity issues from the Winstein rearrangement of the product allylic azides, we initiated our studies using aryl allene 3a (Table 1). Scheme 1. Enantioselective conjugate azidations and hydroazidations. Table 1: Assessment of chiral gold(I) catalysts. Entry Precatalyst Yield [%] ee [%] 1 (R)-DM-SEGPHOS·(AuCl)2 50 20 2 (R)-DTBM-BINAP·(AuCl)2 49 10 3 P1·(AuCl) 35 2 4 N1·(AuCl) 21 5 5 N2·(AuCl) 51 3