Bi(OTf)3-Catalyzed Diastereoselective SN1-Type Reactions of Chiral Propargylic Acetates

An Organometallic Umpolung Approach for Iron-Mediated Propargylic C-H Etherification

Propargylic ethers serve as useful intermediates for the synthesis of a variety of complex targets. However, propargylic substitution of prefunctionalized alkyne starting materials remains the dominant method for the synthesis of propargyl ethers, while direct etherification of simple alkynes via propargylic C-H functionalization remains largely underreported. Herein, we report an organometallic umpolung approach for iron-mediated C-H propargylic etherification. A telescopic protocol for iron-mediated C-H deprotonation followed by mild oxidative coupling with alcohols enabled the use of simple or functionalized alkynes for the expedient synthesis of propargylic ethers with excellent functional group compatibility, chemoselectivity and regioselectivity.

Quaternary and Tertiary Carbon Centers Synthesized via Gallium-Catalyzed Direct Substitution of Unfunctionalized Propargylic Alcohols with Boronic Acids

(IPr)GaCl₃/AgSbF₆, AgSbF₆, and GaCl₃ catalyzed substitution of the hydroxyl of secondary and tertiary propargylic alcohols with organoboronic acids via C-C bond formation, and GaCl₃ effectively synthesized all-carbon quaternary propargylic centers. These catalysts performed the substitution at carbons bearing alkyl substituents, which has been problematic for other systems. Highly hindered carbon stereocenters were thus produced, including quaternary centers bearing doubly ortho-substituted aryl rings, that are difficult to access with traditional methods.

The β-Silyl Effect on the Memory of Chirality in Friedel-Crafts Alkylation Using Chiral α-Aryl Alcohols

Iron salt-catalyzed Friedel-Crafts alkylation of chiral α-aryl alcohols with a trimethylsilyl group was found to proceed with retention of the configuration of the hydroxyl group as a leaving group. The memory of chirality of this system stems from the β-silyl effect of the trimethylsilyl group on the carbocation intermediate.

Sulfoxide-Directed Metal-Free ortho-Propargylation of Aromatics and Heteroaromatics

A sulfoxide-directed, metal-free ortho-propargylation of aromatics and heteroaromatics exploits intermolecular delivery of a propargyl nucleophile to sulfur followed by an intramolecular relay to carbon. The operationally simple cross-coupling procedure is general, regiospecific with regard to the propargyl nucleophile, and shows complete selectivity for products of ortho-propargylation over allenylation. The use of secondary propargyl silanes allows metal-free ortho-coupling to form carbon–carbon bonds between aromatic and heteroaromatic rings and secondary propargylic centres. The ‘safety-catch’ nature of the sulfoxide directing group is illustrated in a selective, iterative double cross-coupling process. The products of propargylation are versatile intermediates and they have been readily converted into substituted benzothiophenes.

Bi(OTf)3-catalyzed three-component synthesis of α-amino acid derivatives

A highly efficient Bi(OTf)3-catalyzed multicomponent synthesis of arylglycines from readily available starting materials is described. The reaction proceeds under mild conditions and provides a general route to various N-protected arylglycines.

Bi(OTf)3-catalysed synthesis of substituted indanes by a double hydroarylation of unactivated 1,3-dienes

A straightforward synthesis of indane derivatives by sequential hydroarylation of 1,3-dienes catalysed by bismuth(iii) triflate is presented.

New trends in bismuth-catalyzed synthetic transformations

This review covers uses of bismuth catalysts since 2005 with a special emphasis on the emerging applications of such catalysts. Low toxicity, low catalytic loading, synergistic effects with other catalysts, and some hydrocompatibility properties confer to bismuth salts major advantages. The expanding activity in the field clearly highlights the growing potential of bismuth catalysts. The article is not a comprehensive review on bismuth catalysis but a selection of its most promising uses in challenging synthetic transformations.

Titanocene-catalyzed multicomponent coupling approach to diarylethynyl methanes

A titanocene-catalyzed multicomponent coupling to provide diarylethynyl methanes is described. By combining the multifunctionality of Cp(2)TiCl(2) with the traceless dielectrophilicity of aryl aldehydes, all-carbon tertiary centers are obtained in 55-99% yield.

Applications of bismuth(III) compounds in organic synthesis

This review article summarizes the applications of bismuth(III) compounds in organic synthesis since 2002. Although there are an increasing number of reports on applications of bismuth(III) salts in polymerization reactions, and their importance is acknowledged, they are not included in this review. This review is largely organized by the reaction type although some reactions can clearly be placed in multiple sections. While every effort has been made to include all relevant reports in this field, any omission is inadvertent and we apologize in advance for the same (358 references).

Bismuth salts in catalytic alkylation reactions

Alkylation reactions utilizing nontoxic Lewis acid catalysts and "green" alkylating reagents are of high interest due to the continuous need for environmentally benign C-C and C-X bond formation. This article shows recent advances in Bi(III)-catalyzed alkylations of arenes, 2,4-pentanediones and various oxygen- and nitrogen-containing nucleophiles. Instead of toxic alkyl halides, the electrophilic components for these transformations were benzyl and propargyl alcohols as well as substrates with activated double bonds such as styrenes. The fact that Bi(III) salts are capable of activating both σ- and π-donors highlights their unique character as versatile catalysts for catalytic alkylation reactions. In addition, Bi(III) salts are less toxic and cheaper than other Lewis acids that have been described for similar transformations.