4-Amino-1-allenylsilanes from 4-Aminopropargylic Acetates through a Silylzincation/Elimination Sequence

Abstract

4-Aminopropargylic acetates afford 4-amino-1-allenylsilanes upon reaction with the lithium (triorganosilyl)zincate (PhMe2Si)3ZnLi. The reaction is both stereoselective and stereospecific and proceeds through syn-silylzincation of the carbon–carbon triple bond followed by subsequent anti-β-elimination of the acetate group.

β‐Amino Propargylic Fluorides through Stereoselective Electrophilic Fluorodesilylation of 4‐Amino‐1‐allenylsilanes

“…With the optimal conditions in hands, the scope of the electrophilic fluorodesilylation was further investigated ( Table 2). 1,4-Syn-4-amino-1-allenylsilanes 3b-f, here prepared as single diastereomers (dr > 98:2) directly from anti-4-amino propargylic acetates by propargylic substitution with (Me 2 PhSi) 3 ZnLi, [9,14] afforded -amino propargylic fluorides 4b-f with high diastereoselectivities (dr ≥ 83:17) as the major products. In all cases, the corresponding side products 5b-f were obtained in about 15 % yield as determined by 19 F NMR analysis of the crude reaction mixtures.…”

“…To gain further insights into the mechanism, we examined the reaction of 1,4‐ anti ‐4‐amino‐1‐allenylsilane 3a′ (diastereomeric to 3a and prepared as a single diastereomer from the corresponding syn ‐4‐amino propargylic acetate) with 2.2 equiv. of Selectfluor® (Scheme ).…”

“…Melting points were measured with a Stuart Scientific SMP3 melting point apparatus. 4‐Amino‐1‐allenylsilanes 3 and 3′ and N‐tert ‐butanesulfinylaziridine 7 were prepared following reported procedures , …”

“…4-Amino-1-allenylsilanes 3 and 3′ and N-tert-butanesulfinylaziridine 7 were prepared following reported procedures. [8,9]…”

“…[3][4][5] The reaction was successfully applied to chiral δ-amino allylsilanes to afford the corresponding -amino allylic fluorides that have been obtained in high yields, albeit with almost no stereoselectivity (Scheme 1b). [6,7] Following on these reports, we reasoned that 4-amino-1allenylsilanes, which are readily accessible stereoselectively through methods reported by our group, [8,9] could be competent partners for the reaction with Selectfluor® and thus offer upon fluorodesilylation a valuable stereoselective access to chiral -amino propargylic fluorides (Scheme 1c). The latter amines are expected to be useful building blocks for the synthesis of fluorinated analogues of nitrogen-containing biomolecules following synthetic routes previously developed in our group.…”