10.1002/ejoc.200800529
The research focuses on the zinc homologation-elimination reaction of α-sulfinyl carbanions as a novel synthetic route to olefins. The study explores the reaction of α-lithiosulfinyl carbanions with zinc carbenoids, which can proceed either intermolecularly through an SN2-type process involving transmetalation into an organocopper derivative or intramolecularly via higher-order zincates through a tandem zinc homologation-β-elimination sequence. The experiments utilize various alkyl sulfoxides as starting materials, which upon treatment with lithium diisopropylamide (LDA) at low temperatures, are transmetalated to form α-sulfinyl copper species. These are then reacted with zinc carbenoids to yield olefins through a β-elimination reaction. The research also investigates the use of DMSO as a source of terminal olefins and explores the intramolecular 1,2-zincate rearrangement as a method to improve the reaction methodology. N,N,N',N'-Tetramethylethylenediamine (TMEDA) and n-BuLi for generating higher-order zincates. The analyses used to characterize the products include NMR spectroscopy, which is detailed in the results section for various synthesized olefins.
10.1002/anie.200460730
The study focuses on the highly diastereoselective nucleophilic addition of the anion derived from α-diazocarbonyl compounds to aromatic N-tosylimines, a reaction that is significant in organic synthesis. The researchers utilized a variety of chemicals, including α-diazocarbonyl compounds (1a-d) with chiral auxiliaries, N-tosylimines (2a-m), and bases such as lithium diisopropylamide (LDA), sodium hexamethyldisilazide (NaHMDS), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). They also experimented with additives like LiCl, MgBr2, and HMPA to enhance stereoselectivity. The purpose of these chemicals was to explore the stereocontrol of the reaction, optimize reaction conditions, and synthesize syn- and anti-α-hydroxy-β-amino esters, which are important building blocks in organic chemistry. The study demonstrated that the diastereoselectivity of the reaction could be significantly improved by the use of HMPA, which likely disrupts ion pairing and allows the α-diazocarbonyl anion to react more efficiently. The results have implications for the synthesis of a range of organic compounds, particularly those containing α-hydroxy-β-amino acid derivatives.
10.1016/S0040-4020(00)00397-5
The study focuses on the stereoselective synthesis and organoleptic properties of p-menthane lactones (7a-h), a class of compounds with significant interest to the perfume industry due to their exceptional odor intensity and typical coumarin-like note. The research corrects published data concerning these compounds and identifies 7a, 7b, and 7g as trace components in Italo Mitcham black peppermint oil (Mentha piperita). Various chemicals were used in the study, including (-)-isopulegol, (+)-neoisopulegol, m-chloroperbenzoic acid, lithium diisopropylamide (LDA), potassium permanganate, Raney nickel, and several others, serving as starting materials, reagents, and catalysts in the synthesis of the lactones. The purpose of these chemicals was to facilitate the synthesis of the p-menthane lactones, allowing for their characterization and evaluation of their sensory properties, which are crucial for their potential use in the perfume and flavoring industries.
10.1055/s-1991-26407
The research aimed to develop a convenient synthesis method for substituted 2-cyano-1,3-butadienes, which are valuable reagents in organic synthesis, particularly for [4+2] cyclo additions. The study focused on the Horner-Emmons olefination of 2-cyano-2-alkenyl- or 2-cyano-3-phenyl-2-propenylphosphonates 1 with selected carbonyl compounds to yield various alkyl or phenyl substituted 2-cyano-1,3-butadienes 2 with high stereoselectivity and satisfactory yield. The process involved the use of lithium diisopropylamide (LDA) in tetrahydrofuran (THF) as a reagent, followed by the reaction with the resultant lithium derivatives and carbonyl compounds. The newly formed double bond consistently had the E configuration, while the formation of the other double bond was not stereoselective, resulting in mixtures of E,E and Z,E isomers. The chemicals used in the process included 2-cyano-2-alkenylphosphonates 1, BuLi (1.6 M solution in hexanes), disopropylamine, and silica gel (70-230 mesh), among others. The conclusion of the research was that an efficient, simple, and general method for the preparation of substituted 2-cyano-1,3-butadienes 2 from readily accessible 2-cyano-2-alkenylphosphonates 1 had been successfully developed.
10.1016/S0040-4020(96)01148-9
The research introduces a novel method for synthesizing α,β'-unsaturated 1,3-diketones using dianions of α'-(trimethylsilyl)enaminones as Peterson reagents. The study aims to achieve regio- and stereoselective control over the formation of the new double bond in these compounds. The key chemicals involved include α'-(trimethylsilyl)enaminones, which are reacted with aldehydes and ketones in the presence of lithium diisopropylamide (LDA) to form the dianions. The reaction conditions, particularly the use of TMEDA (tetramethylethylenediamine) as a lithium complexing agent, significantly influence the product distribution and stereochemistry. The presence of TMEDA favors the formation of the cis isomer, while its absence leads to a mixture of isomers. The study concludes that this method provides a stereoselective route to α,β'-unsaturated enaminones or 1,3-diketones with yields comparable to or better than those achieved by traditional methods such as Claisen condensation or Wittig reactions. The findings suggest that this protocol can be a valuable tool in organic synthesis, especially when a substituent is present in the α position of the enaminone, allowing for regiodirected formation of the double bond.
10.1002/anie.201805203
The study presents a novel ring transposition process for synthesizing highly substituted 2-naphthols and BINOLs using lithium bases, specifically lithium diethylamide (LiNEt2) and lithium diisopropylamide (LDA). The process involves the conversion of readily available coumarins into 2-naphthols through a series of reactions where lithium bases act as both nucleophiles and bases. Initially, the lithium bases facilitate the ring opening of coumarins to form Z-cinnamamides, which serve as in situ directing groups. These Z-cinnamamides, with their conformational freedom, undergo a directed remote metalation and ring closure reaction, yielding aryl 2-naphthols in good to excellent yields. The study also provides mechanistic insights into the remote lateral metalation step, emphasizing the necessity of Z-cinnamamide for the reaction's success. Furthermore, the methodology is applied to the synthesis of highly substituted 3,3’-diaryl BINOL ligands, which are important in enantioselective synthesis and molecular recognition. The purpose of these chemicals is to demonstrate a new synthetic strategy that can efficiently produce complex molecular structures with potential applications in natural products, dyes, pigments, and as ligands and catalysts in asymmetric synthesis.
10.1039/b109269c
The study focuses on the synthesis and application of chiral bisphosphines through a lithiation-conjugate addition tandem cyclization process of chiral a,b,y,w-unsaturated bisphosphine oxides. The researchers used lithium diisopropylamide (LDA) to initiate the cyclization of achiral and chiral a,b,y,w-unsaturated bisphosphonates, yielding endo-a,b-unsaturated cyclic bisphosphine oxides. These were then stereoselectively reduced to produce trans- and cis-bisphosphines, which were successfully applied as chiral ligands in catalytic asymmetric hydrogenation. The chemicals used in the study include LDA, methylenebisphosphonates, diethyl(diphenylphosphoryl)methylphosphonate, and a,y-dialdehydes, which served as precursors and reagents in the synthesis of the chiral bisphosphines. The purpose of these chemicals was to develop a synthetic methodology for chiral bisphosphines, which are valuable as chiral ligands for catalytic asymmetric reactions.
10.1021/ol050558h
The research focuses on the synthesis of D- and L-1,4,6-trideoxy-4,4-difluoronojirimycin, a novel series of gem-difluoromethylenated azasugars. The synthesis involves 10 steps starting from trifluoroethanol, with key chemicals including trifluoroethanol, LDA (lithium diisopropylamide), formaldehyde, MEMCl (2-methoxyethoxymethyl chloride), mesyl chloride, NaN3 (sodium azide), Pd(PPh3)4 (tetrakis(triphenylphosphine)palladium(0)), PPh3 (triphenylphosphine), CbzCl (benzyl chloroformate), SOCl2 (thionyl chloride), and (DHQ)2PHAL or (DHQD)2PHAL (chiral ligands for Sharpless asymmetric dihydroxylation). The synthesis process includes multiple steps such as protection, elimination, vinyl anion formation, sigmatropic rearrangement, allylic substitution, imine formation, Sharpless asymmetric dihydroxylation, and hydrogenation. The final products are obtained with good diastereoselectivity and enantiomeric excess, demonstrating the effectiveness of the synthetic route.
10.1080/00397911.2010.527421
The research aims to develop a novel and efficient method for synthesizing γ-lactone, keto-d-lactone, and butenolide derivatives through the Baeyer–Villiger rearrangement of cyclobutanones. These compounds are significant due to their widespread presence in nature and potential biological activities, making them valuable as intermediates in the synthesis of complex natural products. The study explores the Baeyer–Villiger rearrangement conditions using various cyclobutanones, identifying that freshly prepared peracetic acid with sodium acetate in refluxing CHCl3 provides excellent conversion and good yields. The researchers also developed a one-pot synthesis of keto-d-lactone from the rearrangement products using p-TsOH in refluxing benzene. Additionally, they synthesized butenolide derivatives through a series of reactions involving lithium diisopropylamide (LDA) and PhSeCl, followed by hydrogen peroxide treatment. The study concludes that this method offers a facile and efficient route for the synthesis of these important chemical structures, with potential applications in the total synthesis of natural products like stryllactone. Key chemicals used in the research include cyclobutanone derivatives, peracetic acid, sodium acetate, p-TsOH, NaBH4, LDA, PhSeCl, and hydrogen peroxide.
10.1016/j.tetlet.2011.05.041
The study investigates the reaction of acylsilanes with a-sulfonyl carbanions, such as a-lithioalkyl sulfoxides, to selectively synthesize silyl enol ethers. Acylsilanes, which are silicon-containing compounds with a carbonyl group, react with a-sulfonyl carbanions, generated by treating alkyl or allyl aryl sulfoxides with lithium diisopropylamide (LDA) in tetrahydrofuran (THF) at -78°C. The reaction proceeds through the initial formation of a-silyl alkoxide intermediates, where the silyl group undergoes cationotropic migration to the oxyanion, followed by the elimination of sulfenate anion, yielding silyl enol ethers. Notably, enolizable acylsilanes produce regio-defined silyl enol ethers that cannot be obtained by traditional enolization methods. The study also explores the reaction with a-sulfonyl carbanions derived from alkenyl sulfoxides, yielding 1-silyloxypropadiene derivatives in some cases. The results suggest that the migratory behavior of the silyl group and the nature of the leaving group (such as arylsulfonyl) significantly influence the product selectivity. The study aims to expand the scope and control the stereoselectivity of these reactions for future applications.
