Bismuth-Catalyzed Addition of Silyl Nucleophiles to Carbonyl Compounds and Imines

Abstract

Bismuth triflate was found to be an efficient catalyst both in the Mannich-type reaction of silyl enolates and in the Sakurai reaction of allyltrimethylsilane with N-alkoxycarbonylamino sulfones. The reactions proceeded smoothly with a low catalyst loading of Bi(OTf)(3)·4H(2)O (0.5-5.0 mol%) to afford the corresponding protected β-amino carbonyl compounds and homoallylic amines in very good yields (up to 96%). The latter compounds could also be obtained via a bismuth-mediated three-component reaction. We have also developed an efficient vinylogous Mukaiyama aldol reaction of 2-(trimethylsilyloxy)furan with various aromatic aldehydes mediated by bismuth triflate in a low catalyst loading (1 mol%). The reaction proceeds rapidly and affords the corresponding 5-[hydroxy(aryl)methyl]furan-2(5H)-ones in high yields with good to very good diastereoselectivities (diastereoisomeric ratios>98:2). Such selectivities, although previously reported with other Lewis acids, could be achieved with a much lower catalyst loading. 5-[Hydroxy(alkyl)methyl]furan-2(5H)-ones derived from ketones could also be obtained with good diastereoselectivities. The vinylogous Mukaiyama aldol reaction has also been extended to 2,2-dimethyl-6-methylene-4-(trimethyl-silyloxy)-1,3-diox-4-ene using 1 mol% of Bi(OTf)(3)·4H(2)O.

Bi(I)-Catalyzed Transfer-Hydrogenation with Ammonia-Borane

“…Yet, the use of bismuth in organic synthesis has been largely dominated by stoichiometric reactions based on Bi(V) or Bi(III) species, and catalytic strategies primarily focused on the soft Lewis-acid properties of Bi(III) salts (Figure 1B). 12 In addition, methods beyond the classic reactivity of Bi salts have recently attracted increasing attention. 13 In contrast to the wealth of methods using high-valent Bi species, 14 attention to its low-valent counterparts has been scarce.…”

“…Importantly, Bi has been considered nontoxic and largely more abundant than commonly employed TM such as Pd, Rh or Ir, thus highlighting its potential toward developing truly sustainable catalytic strategies. Yet, the use of bismuth in organic synthesis has been largely dominated by stoichiometric reactions based on Bi­(V) or Bi­(III) species, and catalytic strategies primarily focused on the soft Lewis-acid properties of Bi­(III) salts (Figure B) . In addition, methods beyond the classic reactivity of Bi salts have recently attracted increasing attention .…”

Mechanistic study of the bismuth mediated fluorination of arylboronic esters and further rational design

“…In this respect, the bismuth (Bi) involving complexes have great potential in the field of sustainable catalysis due to the inexpensive and abundant properties of main group bismuth element. 31 However, the employment of bismuth element in catalysis is mainly dependent on its soft Lewis acidity with a fixed oxidation state, 32 rather than its redox capacities. Until so far, the exploitation of bismuth's redox capacities in catalysis, which can access transition-metal reactivity, is still challenging.…”

Lead-Mediated Highly Diastereoselective Allylation of Aldehydes with Cyclic Allylic Halides

“…Also, our initial assessment of the allylation reaction involving 4-chlorobenzaldehyde ( 1a ) and 3-bromocyclohexene ( 2a ) by using lead as the sole reaction mediator showed that the reaction proceeded sluggishly to afford the corresponding product only in 7% yield (Table , entry 1). On the other hand, recent advancements achieved during the course of synthesizing organometallic reagents via direct metal insertion into organohalides , have implied that the addition of additives (e.g., LiX ,, ) and/or catalysts (e.g., InX 3 , ,,, BiX 3 , , and PbX 2 , ) might remarkably facilitate the insertion of metals (e.g., Mg, Zn, Al, and In) into organic halides. Thus, in continuation of our endeavors to develop metal-mediated organic transformations, herein, we report an efficient lead-mediated highly diastereoselective allylation of carbonyl compounds with cyclic allylic halides in the presence of stoichiometric amounts of LiCl and a catalytic amount of GaCl 3 .…”