Stereoselective synthesis of (E)-1-fluoro-1,3-enynes

Simple Synthesis of Fluorinated Ene-Ynes via In Situ Generation of Allenes

Fluorination of small molecules is a key route toward modulating reactivity and bioactivity. The 1,3 ene-yne functionality is an important synthon towards complex products, as well as a common functionality in biologically active molecules. Here, we present a new synthetic route towards fluorinated ene-ynes from simple starting materials. We employ gas chromatography-mass spectrometry analysis to probe the sequential eliminations necessary for this transformation and observe an allene intermediate. The ene-yne products are sufficiently fluorous to enable purification via fluorous extraction. This methodology will allow facile access to functional, fluorous ene-ynes.

Novel Stereoselective Synthesis of (Z)-2-Arylthio-Substituted 1,3-Enynes from (E)-α-Stannylvinyl Sulfides and 1-Alkynes

( E)-α-Stannylvinyl sulfides 1 underwent the iododestannylation reaction with iodine to give the ( E)-α-iodovinyl sulfides 2, which were coupled directly with terminal alkynes 3 without isolation in the presence of Pd(PPh3)4 and CuI co-catalyst to afford stereoselectively ( Z)-2-arylthio-substituted 1,3-enynes 4 in good yields.

Iron-Catalyzed Dehydrative Alkylation of Propargyl Alcohol with Alkyl Peroxides To Form Substituted 1,3-Enynes

This paper reports a new method for the generation of substituted 1,3-enynes, whose synthesis by other methods could be a challenge. The dehydrative decarboxylative cascade coupling reaction of propargyl alcohol with alkyl peroxides is enabled by an iron catalyst and alkylating reagents. Primary, secondary, and tertiary alkyl groups can be introduced into 1,3-enynes, affording various substituted 1,3-enynes in moderate to good yields. Mechanistic studies suggest the involvement of a radical-polar crossover pathway.

Hypervalent iodine(iii) fluorinations of alkenes and diazo compounds: new opportunities in fluorination chemistry

The fluorination of organic molecules is a rapidly evolving and exciting field in synthesis, which still poses huge challenges despite the advances made in the past decades. Hypervalent iodine(iii) reagents, which have already proven their versatility as synthetic tools in organic chemistry, are currently on the rise in fluorination chemistry. With their ability to break new mechanistic grounds, they grant access to completely new reactivities and thus also to novel fluorinated structural scaffolds. This review aims to provide an overview of the achievements made in the iodine(iii) mediated fluorinations of aliphatic Csp²-carbon atoms with special focus on the opportunities provided by this exciting class of hypervalent substances.

Stereoselective synthesis of conjugated fluoro enynes

Metalation-electrophilic fluorination of TMS- and TIPS-protected 1,3-benzothiazol-2-yl (BT) propargyl sulfones gave corresponding BT fluoropropargyl sulfones, Julia-Kocienski reagents for the synthesis of fluoro enynes. Both reagents reacted with aldehydes under mild DBU- or LHMDS-mediated conditions, giving high yields of conjugated fluoro enynes with E-stereoselectivity. In comparison to DBU-mediated reactions, stereoselectivity was higher in low-temperature LHMDS-mediated reactions. Two ketones were shown to react as well, using LHMDS as base. In situ removal of the TMS group gave terminal conjugated 2-fluoro 1,3-enynes. Synthetic utility of the fluoro enynes was demonstrated by conversion to internal alkynes and to stereoisomeric fluoro dienes via Sonogashira and Heck couplings.

Site-Selective Suzuki-Miyaura and Sonogashira Cross Coupling Reactions of the Bis(triflate) of 2,4'-Bis(hydroxy)diphenyl Sulfone

Described is the synthesis of novel arylated and alkynylated 2,4′‐diphenyl sulfones based on what are, to the best of our knowledge, the first palladium(0)‐catalyzed cross‐coupling reactions of bis(triflates) of 2,4′‐bis(hydroxy)diphenyl sulfone. The reactions proceed with very good site‐selectivity.

A Facile Stereoselective Synthesis of (Z)-2-ethoxycarbonyl-substituted 1,3-enynes from (E)-α-stannyl-α,β-unsaturated esters and alkynyl bromides

Palladium-catalysed hydrostannylation of alkynyl esters in benzene at room temperature gives regio- and stereoselectively ( E)-α-stannyl-α,β-unsaturated esters in good yields. ( E)-α-Stannyl-α,β-unsaturated ethyl esters are difunctional group reagents which undergo Stille coupling reactions with alkynyl bromides in the presence of Pd(PPh3)4 and Cul co-catalyst to afford stereoselectively ( Z)-2-ethoxycarbonyl-substituted 1,3-enynes in good yields.

A Facile Stereoselective Synthesis of (Z)-2-arylsulfonyl-substituted 1,3-enynes from (E)-α-stannylvinyl Sulfones and Alkynyl Bromides

Palladium-catalysed hydrostannylation of acetylenic sulfones 1 in benzene at room temperature gives stereoselectively (E)-α-stannylvinyl sulfones 2 in good to high yields. (E)-α-Stannylvinyl sulfones 2 are difunctional group reagents which undergo cross-coupling reactions with alkynyl bromides 3 in the presence of Pd(PPh3)4 and CuI co-catalyst to afford stereoselectively (Z)-2-arylsulfonyl-substituted 1,3-enynes 4 in good yields.

Stereoselective synthesis of (Z)-2-fluoro-1-alkenyl(phenyl)iodonium tetrafluoroborates

[reaction: see text] (Z)-2-Fluoro-1-alkenyl(phenyl)iodonium salts were stereoselectively prepared by the reaction of alkynyl(phenyl)iodonium salts with aqueous HF in good yields. The method is applicable to the synthesis of fluoroalkenyliodonium salts having functional groups such as ketone, ester, and chloride. (Z)-2-Fluoro-1-alkene, (Z)-2-fluoro-2-alkenoate, and (Z)-beta-fluoroenyne could be stereoselectively prepared from the fluoroalkenyliodonium salt.