A Catalytic Asymmetric Borono Variant of Hosomi–Sakurai Reactions with N,O‐Aminals

Abstract

Aminal attraction: The combination of indium(I) chloride and a chiral silver binol phosphate provides an excellent catalyst for asymmetric Hosomi–Sakurai reactions between N,O‐aminals and boronates (see scheme; PG=protecting group, pin=pinacolato). The substrate scope includes aromatic, heteroaromatic, and aliphatic N,O‐aminals as well as allyl and allenyl boronates.

Univalent Gallium and Indium Phosphane Complexes: From Pyramidal M(PPh3)3+ to Carbene‐Analogous Bent M(PtBu3)2+ (M=Ga, In) Complexes

“…[6] Recent achievements have included the synthesis of unusual coordination compounds and metal clusters of fundamental interest, as well as applications in the fields of catalysis and polymerization, [7][8][9] for example, using In I catalysts for the allylboration of ketones [10] or to form asymmetric CÀC bonds. [11] Simple univalent In I salts are less common than their trivalent counterparts and are often unstable: InF only exists in the gas phase at high temperature, whereas InCl, InBr, and InI are stable solids under ambient conditions that are sparingly soluble in organic solvents. However, InBr dissolves in a mixture of tetramethylethylenediamine (tmeda) and toluene below À20 8C.…”

Gallium and Indium Compounds in Homogeneous Catalysis

“…98 Control experiments support the in situ formation of a chiral In(I) species as the active catalyst. The reaction is thought to follow a S N 1 pathway via a nucleophilic attack of the allyl boronate on an iminium intermediate.…”

Grignard Reactions in Cyclopentyl Methyl Ether

“…To this solution was added benzaldehyde (3; 1.06 g, 9.99 mmol) in CPME (10 mL) through ac annula and the mixture was stirred for 1hat room temperature. The reaction mixture was quenched by the sequential addition of saturated aqueous NH 4 Cl solution and saturated Rochelle salt solution at 0 8C. The resulting mixture was extracted with CPME (3 30mL), and the combined organic layers were washed with brine, dried over anhydrous MgSO 4 and filtered (rinsed with CPME).…”

“…CPME was recovered by distillation under reduced pressure (b.p. 40-50 8C, 13-17 kPa), transferred to ab rown-colored bottle and kept at room temperature after addition of molecular sieves (4 ). The residue was purified by flash chromatography on silica gel (n-hexane/EtOAc, 5:1v/ v) to give alcohol 4j (2.05 g, 9.37 mmol, 94 %b ased on 3)a sapale yellow oil.…”

“…[1] About ten years ago, the Zeon Corporation introduced the other green hydrophobic ether,c yclopentyl methyle ther (CPME), as an alternative to conventional ether solvents. [3] Its application in organic synthesis has increasingly broadened, [4] and in somecases betters electivity was obtained with this solvent system. [5] We independently reported that CPME served as ar adical reaction solventa nd demonstrated an umber of radicalr eactions including radical additions, radicald eoxygenations, radical cyclizations,a nd radical-containingo ne-pot reactions.…”