Synthesis of 4‑Vinylindoles Using Ruthenium-Catalyzed Ring-Closing Enyne Metathesis

The selective synthesis of substituted 4-vinylindoles by the ring-closing enyne metathesis (RCEM)/dehydration sequence is reported. In contrast with many known methods in which a pyrrole ring is constructed onto a functionalized benzene precursor, this method enables the construction of a benzene ring onto a pyrrole precursor. The RCEM/tautomerization sequence for the synthesis of 7-hydroxy-4-vinylindole is also presented as an application of this method

Catalytic Asymmetric Three-Component Mannich-Type Reaction of Alkenyl Trichloroacetates

A catalytic enantioselective three-component Mannich-type reaction of alkenyl trichloroacetates, ethyl glyoxalate, and aniline derivatives was achieved using an (S)-BINOL-derived chiral tin dibromide possessing a 4-trifluoromethylphenyl group at the 3- and 3′-positions as the chiral precatalyst in the presence of sodium ethoxide, sodium iodide, and ethanol. Optically active β-amino ketones with up to 98% ee were syn-selectively obtained in high yields even from imines possessing a polar amino group under the influence of the in situ generated chiral tin bromide ethoxide

Selective Synthesis of α,β-Unsaturated Ketones by Dibutyltin Dimethoxide-Catalyzed Condensation of Aldehydes with Alkenyl Trichloroacetates

Various α,β-unsaturated ketones were stereoselectively synthesized in high yields up to 94% by a condensation reaction between alkenyl trichloroacetates and aldehydes using dibutyltin dimethoxide as a catalyst in the presence of methanol. This process is superior to the classical Claisen−Schmidt condensation with respect to mildness of the base catalyst and product selectivity

Practical Asymmetric Henry Reaction Catalyzed by a Chiral Diamine-Cu(OAc)₂ Complex

The chiral diamine ligand 3 was designed and synthesized from (R,R)-1,2-diphenylethylenediamine, (S)-2,2‘-dibromomethyl-1,1‘-binaphthalene, and o-xylylene dibromide. The resulting 3-Cu(OAc)2 complex was a highly efficient catalyst for the Henry reaction, giving the various nitroaldols with over 90% ee (up to >99%). The reaction was performed in n-propyl alcohol at room temperature, and the Henry adducts were produced in high yield with excellent enantiomeric excess; these attributes are desirable in a catalyst for practical use

Synthesis of Carbocyclic Aromatic Compounds Using Ruthenium-Catalyzed Ring-Closing Enyne Metathesis

General synthetic methods of substituted carbocyclic aromatic compounds are reported. Ring-closing enyne metathesis (RCEM)/dehydration of 1,5-octadien-7-yn-4-ols 6 and RCEM/tautomerization of 1,5-octadien-7-yn-4-ones 7 furnished a wide variety of substituted styrenes 4 and 4-vinylphenols 8, respectively. Acyclic precursors 6 and 7 were readily prepared from β-halo-α,β-unsaturated aldehydes 9 or 3-halo-2-propene-1-ols 13 by utilizing combinations of the Sonogashira coupling, allylation, and the Dess−Martin oxidation. The RCEM/dehydration for the synthesis of 1,3,5-tris(1-phenylethenyl)benzene derivative 4r and the RCEM/RCM/dehydration for the synthesis of 1,1′-binaphthyl derivative 19a are also presented as applications of this method

Catalytic Enantioselective Synthesis of Chiral γ-Butyrolactones

A tandem catalytic asymmetric aldol reaction/cyclization of β,γ-didehydro-γ-lactones with aldehydes was achieved using chiral tin dibromide as a chiral precatalyst and sodium alkoxide as a base precatalyst. Optically active trans-β,γ-disubstituted γ-butyrolactones were selectively obtained in moderate to high yields with up to 99% ee from γ-aryl-substituted β,γ-didehydro-γ-butyrolactones and bulky aliphatic aldehydes

Catalytic Asymmetric Three-Component Mannich-Type Reaction of Alkenyl Trichloroacetates

A catalytic enantioselective three-component Mannich-type reaction of alkenyl trichloroacetates, ethyl glyoxalate, and aniline derivatives was achieved using an (S)-BINOL-derived chiral tin dibromide possessing a 4-trifluoromethylphenyl group at the 3- and 3′-positions as the chiral precatalyst in the presence of sodium ethoxide, sodium iodide, and ethanol. Optically active β-amino ketones with up to 98% ee were syn-selectively obtained in high yields even from imines possessing a polar amino group under the influence of the in situ generated chiral tin bromide ethoxide

Catalytic Enantioselective Synthesis of Chiral γ-Butyrolactones

A tandem catalytic asymmetric aldol reaction/cyclization of β,γ-didehydro-γ-lactones with aldehydes was achieved using chiral tin dibromide as a chiral precatalyst and sodium alkoxide as a base precatalyst. Optically active trans-β,γ-disubstituted γ-butyrolactones were selectively obtained in moderate to high yields with up to 99% ee from γ-aryl-substituted β,γ-didehydro-γ-butyrolactones and bulky aliphatic aldehydes

Reaction Optimization Using Solid-Phase Catalysis-CD HTS: <i>N</i>b-Imidazoline−Cu(I)-Catalyzed Asymmetric Benzoylation of 1,2-Diols

Catalytic asymmetric benzoylation of 1,2-diols has been developed using a solid-phase asymmetric catalyst. The reaction conditions were optimized by the screening of different metal salts, solvents, bases, and temperatures. High-throughput screening was performed using circular dichroism detection, and the results revealed that Nb-imidazoline−copper(I) in combination with diisopropylethylamine was able to catalyze with high enantioselectivity, giving the monobenzoylated products in high yields and excellent enantiomeric excesses of up to 95% ee

Construction of Carbocyclic Ring of Indoles Using Ruthenium-Catalyzed Ring-Closing Olefin Metathesis

The selective synthesis of substituted indoles was achieved by the ring-closing olefin metathesis (RCM)/elimination sequence or the RCM/tautomerization sequence of functionalized pyrrole precursors. The RCM/elimination sequence was also applied to double ring closure to yield a substituted carbazole