Alkenyltrifluoroborate Salts Research Articles

Enantioselective Conjugate Addition of Alkenyl Trifluoroborates to Alkenyl-Substituted Benzimidazoles Catalyzed by Chiral Binaphthols.

The enantioselective organocatalytic conjugate alkenylation of β-substituted alkenyl benzimidazoles afforded β-stereogenic 2-alkyl benzimidazole derivatives in excellent enantioselectivities. Chiral binaphthols were effective catalysts for promoting the nucleophilic addition of bench-stable alkenyl trifluoroborate salts under mild conditions, expanding their applications by utilizing C=N-containing azaarenes as activating groups. The synthetic utility of this strategy is demonstrated by conversions into several useful enantiomerically enriched benzimidazole building blocks.

Enantioselective synthesis of α-amino esters through Petasis borono-Mannich multicomponent reaction of potassium trifluoroborate salts

Enantioselective synthesis of α-amino esters have been achieved through the Petasis borono-Mannich multicomponent reaction using ( R)-BINOL-derived catalysts with stable heteroaryl and alkenyl trifluoroborate salts under mild conditions. The reaction provides direct access to optically active α-amino esters with moderate to good yields and enantioselectivities.

Brønsted Acid-Catalyzed Reactions of Trifluoroborate Salts with Benzhydryl Alcohols

Brønsted acid-catalyzed carbon-carbon bond forming methodology using potassium alkynyl- and alkenyltrifluoroborate salts has been developed. Organotrifluoroborates react with benzhydryl alcohols to afford a broad range of alkynes and alkenes in good to excellent yields. This protocol features good atom economy because organotrifluoroborate salts and alcohols react in a 1:1 ratio. Furthermore, a variety of unprotected functional groups were tolerated under the developed conditions, including amide, aldehyde, free hydroxyl, and carboxylic acid.

ChemInform Abstract: Synthesis of α‐Alkenyl‐α‐amino Esters via Addition of Potassium Alkenyltrifluoroborate Salts to Imine in the Presence of Yb(OTf)3.

AbstractN‐Aryl‐substituted α‐imino esters and various alkenyltrifluoroborates are found to undergo Lewis‐acid‐catalyzed C‐alkenylation reaction to give varying yields of α‐alkyl‐α‐amino esters.

ChemInform Abstract: Copper‐Catalyzed Nondecarboxylative Cross Coupling of Alkenyltrifluoroborate Salts with Carboxylic Acids or Carboxylates: Synthesis of Enol Esters.

A mild copper-catalyzed Chan–Lam–Evans type cross-coupling reaction for the regioselective and stereospecific preparation of (E)- or (Z)-enol esters is described. The method couples carboxylate salts or carboxylic acids with potassium alkenyltrifluoroborate salts in the presence of catalytic CuBr and DMAP with 4 A molecular sieves under O2 at 60 °C. Overall, this method demonstrates carboxylic acids as suitable reaction partners for nondecarboxylative copper-catalyzed cross-couplings to form C–O bonds in an Ullmann-like reaction.

Synthesis of α-alkenyl-α-amino esters via addition of potassium Alkenyltrifluoroborate salts to imine in the presence of Yb(OTf)3

A simple protocol which led to an effective construction of α-alkenyl-α-amino esters was achieved under mild conditions. This transformation proceeded by Yb-catalyzed addition of alkenyltrifluoroborates across the imine double bond. A variety of functional groups could be applicable to both partners.

Copper-Catalyzed Nondecarboxylative Cross Coupling of Alkenyltrifluoroborate Salts with Carboxylic Acids or Carboxylates: Synthesis of Enol Esters

A mild copper-catalyzed Chan-Lam-Evans type cross-coupling reaction for the regioselective and stereospecific preparation of (E)- or (Z)-enol esters is described. The method couples carboxylate salts or carboxylic acids with potassium alkenyltrifluoroborate salts in the presence of catalytic CuBr and DMAP with 4 Å molecular sieves under O2 at 60 °C. Overall, this method demonstrates carboxylic acids as suitable reaction partners for nondecarboxylative copper-catalyzed cross-couplings to form C-O bonds in an Ullmann-like reaction.

ChemInform Abstract: Copper‐Catalyzed Cross‐Coupling of Amides and Potassium Alkenyltrifluoroborate Salts: A General Approach to the Synthesis of Enamides.

AbstractTwo sets of reaction conditions are developed depending on the pKa of the amide.

Copper-catalyzed cross-coupling of amides and potassium alkenyltrifluoroborate salts: a general approach to the synthesis of enamides

Potassium alkenyltrifluoroborate salts undergo coupling with amides to give enamides using a catalytic amount of Cu(OAc) 2 under mild oxidative conditions. The air and water stable alkenyltrifluoroborate salts offer a practical alternative to the use of alkenyl halides and alkenylboronic acids as cross-coupling partners. A range of amides participate in the cross-coupling, including heterocyclic amides, imides, carbamates, benzamides, and acetamides. Optimization studies established two sets of conditions, best suited to either high p K a or low p K a amide substrates. Lower p K a amide substrates worked best using a dichloromethane solvent system in the presence of 4 Å molecular sieves, 10 mol % Cu(OAc) 2, and 20 mol % N-methylimidazole. Higher p K a amide substrates worked best using a ‘ligandless’ protocol using a 1:1 dichloromethane/DMSO solvent system in the presence of 4 Å molecular sieves and 10 mol % Cu(OAc) 2. The cross-coupling reactions occur stereospecifically with retention of alkene configuration from the alkenyltrifluoroborate salt. The mild reaction conditions employed are tolerant of various functionalities, including nitro, acetals, alkyl and aryl halides, and α,β-unsaturated carbonyls. Finally, the importance of copper sources and the presence of minor impurities were investigated.

Asymmetric Synthesis of α-Branched Allylic Amines by the Rh(I)-Catalyzed Addition of Alkenyltrifluoroborates to N-tert-Butanesulfinyl Aldimines

The first Rh(I)-catalyzed addition of alkenylboron reagents to imines is described. The Rh(I)-catalyzed addition of potassium alkenyltrifluoroborate salts to both aromatic and aliphatic N-tert-butanesulfinyl aldimines proceeds in good yields (up to 97%) and with very high diastereoselectivities (95:5 to >99:1). This new method enables the general and efficient asymmetric synthesis of the important class of alpha-branched allylic amines from readily available and stable starting materials.

Rhodium(I)-Triethylamine-Catalyzed 1,4-Addition of Enones

The authors describe a highly efficient rhodium-catalyzed 1,4-addition of alkenyl trifluoroborate salts to cyclic enones in the presence of triethylamine. Notably, they found that the use of triethylamine enhanced both reactivity and enantioselectivity. Mechanistic studies revealed that triethylamine forms a complex with rhodium, which serves as the active catalyst because it accelerates the B-Rh transmetalation reaction by displacement of the original ligand on Rh. In addition, it is noteworthy that the authors could achieve the first rhodium-catalyzed 1,4-addition of a (Z)-alkyl-substituted terminal alkenyl group to enones.

ChemInform Abstract: Enamide Synthesis by Copper‐Catalyzed Cross‐Coupling of Amides and Potassium Alkenyltrifluoroborate Salts.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Enamide Synthesis by Copper‐Catalyzed Cross‐Coupling of Amides and Potassium Alkenyltrifluoroborate Salts

A new partner: Potassium alkenyltrifluoroborate salts undergo coupling with amides to give enamides in the presence of a Cu(OAc)2 catalyst and under mild oxidative conditions (see scheme). The air- and water-stable alkenyltrifluoroborate salts offer a convenient alternative to alkenyl halides as cross-coupling partners. A range of amides undergo coupling including cyclic amides, imides, and carbamates as well as benzamides.

Enamide Synthesis by Copper‐Catalyzed Cross‐Coupling of Amides and Potassium Alkenyltrifluoroborate Salts

Enamide Synthesis by Copper‐Catalyzed Cross‐Coupling of Amides and Potassium Alkenyltrifluoroborate Salts

Organoboron compounds as mild nucleophiles in Lewis acid- and transition metal-catalyzed C­C bond-forming reactions

Abstract The use of air- and water-stable organoboron compounds for C­C bond-forming reactions are reported. These studies include the Lewis acid-promoted additions of boronic esters to N-acyliminium ions and allyl and crotyltrifluoroborate salts to aldehydes. Aryl and alkenyltrifluoroborate salts will add to aldehydes under the influence of rhodium catalysis or in the presence of zinc metal. These salts also participate in palladium-catalyzed Suzuki­Miyaura and other cross-coupling reactions. Finally, a new type of N-heterocyclic carbene ligand is reported and used for Pd-catalyzed Suzuki­Miyaura couplings.