Yttrium‐Catalyzed Intermolecular Anti‐Markovnikov Hydroamination and Sequential Intermolecular Hydroamination/Endocyclization of Vinylsilanes

Abstract

The intermolecular anti‐Markovnikov hydroamination of vinylsilanes was achieved utilizing five silyl‐substituted ortho‐terphenoxide yttrium complexes. The highest activity was observed for the most sterically encumbered triphenylsilyl‐substituted complex. Excellent activity and complete anti‐Markonikov selectivity were obtained for a variety of benzylic and aliphatic primary and secondary amines. Interestingly, the reaction with 2‐picolylamine produced the hydroaminoalkylation product rather than the hydroamination product. Reaction of dimethyldivinylsilane resulted in a range of 1,4‐azasilinanes via sequential hydroamination/endocyclization in good yields.

Silyl‐Substituted ortho‐Terphenoxide Group 3–5 Complexes: Synthesis, Structure and Applications in Catalysis

“…The ortho-terphenoxide ligands 1 a-d were synthesized as reported earlier. [15] The hydroamination substrates were distilled from finely powdered CaH 2 and stored over 4 Å molecular sieves in the glovebox. If not mentioned otherwise, all commercially available starting materials were used without further purification.…”

“…Moreover, the angles are comparable to the previously reported yttrium complex IIIb (98.78(9)°). [15] In both cases, the amido ligand is unsymmetrically bound, with one silicon in closer proximity to the metal center and different YÀ NÀ Si bond angles (Table 1), with the Y1-N1-Si4…”

“…Figure 1. Titanium and yttrium ortho-terphenoxide complexes [14,15] Scheme 1. Formation of yttrium complexes 2 a, 2 b and 2 d. angle being more acute.…”

“…The ortho-terphenoxide yttrium aryl complexes IIIa-d have shown activity in the intermolecular hydroamination of vinylsilanes. [15] The most sterically encumbered yttrium complex IIIa demonstrated the highest catalytic activity, hence herein we used the corresponding complex 2 a for our catalytic studies. Complex 2 a demonstrated its applicability in the intramolecular hydroamination of aminoalkenes (Table 4), cyclizing both the gem-diphenyl-substituted aminopentene 8 a and (1allylcyclohexyl)methanamine (8 b) in good yields under mild conditions.…”

“…In a separate study, related orthoterphenoxide yttrium aryl complexes IIIa-d have been investigated with respect to their catalytic activity in the intermolecular hydroamination of vinylsilanes. [15] Results and Discussion…”