A novel synthesis of β-lactone precursors of pyramidalized alkenes

β-Lactone precursors 11 and 12 of pyramidalized alkenes 3,n = 1and 2, have been synthesized by a two-step route involving transannular Paterno-Buchi reaction of methyleneketones 7 and 8, followed by RuO₄ oxidation of the resulting oxetanes 9 and 10. Evidence for the formation of alkene 3,n = 2, by pyrolysis of 12 is presented.     

Acetonitrile-dependent oxyphosphorylation: A mild one-pot synthesis of β-ketophosphonates from alkenyl acids or alkenes

An efficient one-pot synthesis of β-ketophosphonates has been developed, via the reaction of α,β-alkenyl carboxylic acids or alkenes with H-phosphonates and air oxygen, catalyzed by CuSO₄·5H₂O in CH₃CN. CH₃CN plays a decisive role, probably by forming an active oxygen complex [(MeCN)_nCu^II-O-O·].     

A facile synthesis of trisubstituted alkenes from β-diketones and aldehydes with AlCl3 as catalyst

Preparation of trisubstituted alkenes from low-activity β-diketones and aldehydes with aluminum chloride as catalyst has been studied. The frequently used catalyst AlCl₃ is used for the first time to promote this condensation. The procedure is a convenient, low toxicity, and highly efficient method for industrial synthesis of trisubstituted alkenes in high yield.     

Practical synthesis of β-isothiocyanato ketones from chalcones

Practical synthesis of 1,3-diaryl-substituted 3-isothiocyanatopropan-1-ones based on the reaction of chalcones with thiocyanic acid generated in situ by treatment of thiocyanate ammonium with dilute sulfuric acid has been developed.     

Two-step synthesis of β-alkyl chalcones and their use in the synthesis of 3,5-diaryl-5-alkyl-4,5-dihydropyrazoles

We report a simple and efficient two-step synthesis of variously substituted β-alkyl chalcones (7) from the corresponding Weinreb amide and a terminal alkyne, and that these chalcones are useful intermediates for the synthesis of medicinally interesting 3,5-diaryl-5-alkyl-4,5-dihydropyrazoles (6). The current methodology allows for the incorporation of many substitution patterns not available from the few previously reported approaches to compounds in this class.     

Direct synthesis of β-ketophosphine oxides via copper-catalyzed difunctionalization of alkenes with H-phosphine oxides and dioxygen

A simple copper-catalyzed direct difunctionalization of alkenes with H-phosphine oxides and dioxygen for the synthesis of β-ketophosphine oxides has been developed under mild conditions. The present protocol, which utilizes an inexpensive catalyst, readily available materials, and environmentally benign oxygen source, provides a convenient and cost-effective approach to construct various β-ketophosphine oxides.     

Enantioselective synthesis of β-substituted cyclic ketones via cobalt-catalyzed asymmetric reductive coupling of alkynes with alkenes

A CoI(2)/(R)-BINAP, Zn, ZnI(2), H(2)O system efficiently catalyzes the intermolecular asymmetric reductive coupling of alkynes with cyclic enones to afford highly regio- and enantioselective β-alkenyl cyclic ketones. A possible mechanism that involves the formation of a cobaltacyclopentene intermediate from the alkyne and cyclic enone is proposed.     

Metal-free,PTSA catalyzed facile synthesis of β-ketoacetal from β-chlorocinnamaldehyde

A toluene solution of β-chlorocinnamaldehyde and dihydroxy alcohols in the catalytic presence of para-toluenesulphonic acid (PTSA) yield the β-ketoacetal in good to outstanding amount. The catalyst (PTSA), first selectively protect the aldehydic group to form the β-chloroacetal and the subsequent dechlorination by H₂O result the β-ketoacetal. Significant transformation was achieved with electron donating substituent attached at the para-position of cinnamaldehyde. The selective formation of β-keto-1,3-acetal was also obtained with a mixture of 1, 2- and 1, 3- diol. The present reaction consists of a metal-free, economical, robustly feasible, sizeable functional group tolerance and high yield properties. Moreover, the use of different dihydroxy alcohols made this process more benign and valuable towards the metal-free development of ketones. First, of its kind, a rare and unusual multitasking nature of PTSA is observed.     

Highly diastereoselective indium-mediated synthesis of β-lactam carbohydrates from imines

A simple and very effective approach to versatile carbohydrate β-lactam synthons of predictable absolute configuration has been developed. The procedure, which is based on the indium-mediated reaction of imines and bromoesters, was applied to the enantioselective synthesis of 3-monosubstituted and 3-disubstituted β-lactams from readily available carbohydrates. The opening of the β-lactamic ring gave rise to the corresponding sugar-derived β-amino acids. Transformation of the β-lactams into the corresponding azetidines was also achieved.     

A convenient synthesis of vinyl sulfoximines from β-hydroxyalkyl sulfoximines

Previously unknown free and N-acylated vinyl sulfoximines were readily prepared via elimination of β-hydroxyalkyl methylphenylsulfoximines.     

Selective synthesis of β-alkylpyrroles

β-Alkylpyrroles are key structural motifs found in many natural products and biologically active compounds as well as functional organic materials. For this reason, synthetic chemists continue to be interested in construction of the framework of β-alkylpyrroles. Due to sufficient aromaticity and π-excessive nature of pyrroles, a straightforward approach to β-alkylpyrroles should be electrophilic aromatic substitution (S(E)Ar) toward the pyrrole ring. However, since a primary nucleophilic site of pyrroles is an α-position, some "trick" is required to direct incoming alkyl electrophiles toward a β-position. This Concept article focuses on presenting previous efforts that have been devoted to the synthesis of β-alkylpyrroles, mainly through the S(E)Ar route.     

One-pot synthesis of β-imidazolylpropionamides

New efficient one-pot methodology for the preparative synthesis of β-imidazolylpropionamides was elaborated. It is based on the addition of imidazole to the activated double bond of the intermediate acrylimidazolide in the reaction between diverse acrylic acids and different amines promoted by CDI. A set of structurally and functionally diverse β-imidazolylpropionamides was obtained in high preparative yields.     

Enantioselective synthesis of β-amino-diacids

An efficient route to orthogonally protected β-amino-diacids is described: chiral derivative 3 was shown to be a precursor of enantiopure substituted β-amino acids. The key step of the procedure is a diastereoselective reduction of β-enaminolactones 5 by NaBH₃CN in CH₂Cl₂. A study concerning the regio- and diastereoselectivity of alkylation of β-enaminolactone 3 is also presented.     

H-β-zeolite catalyzed synthesis of β-bromostyrenes from styrene bromohydrins

Synthesis of β-bromostyrenes from styrene bromohydrins using H-β-zeolite as catalyst under moderate conditions is reported. The catalyst could be regenerated and reused up to three consecutive cycles.     

Metal-free tetra-n-butylammonium bromide-mediated aerobic oxidative synthesis of β-ketosulfones from styrenes

An efficient and broadly applicable protocol for the aerobic coupling of styrenes with sulfonylhydrazides has been developed that affords P-ketosulfones bearing various functional groups in moderate to excellent yields.The preliminary experimental results support the involvement of active benzyl radical species,and a radical pathway was therefore proposed for the reaction.     

Regioselective synthesis of polysubstituted 4H-thiopyrans from β-oxodithioesters

A simple and efficient method for the synthesis of polyfunctionalized 4H-thiopyrans by highly regioselective cyclocondensation of β-oxodithioesters with 1,1,3-trialkyl or aryl substituted prop-2-yn-1-ols using BF₃·Et₂O as the catalyst is described.     

Efficient synthesis of β-chlorovinylketones from acetylene in chloroaluminate ionic liquids

A method for the Friedel-Crafts-type insertion reaction of acetylene with acid chlorides in chloroaluminate ionic liquids is presented. The use of ionic liquids not only serves to avoid the use of carbon tetrachloride or 1,2-dichloroethane but also suppresses side reactions, notably the polymerization of acetylene, which occurs in these chlorinated solvents. Consequently, the products can be isolated using a simpler purification procedure, giving a range of aromatic and aliphatic β-chlorovinyl ketones in high yield and purity.     

Asymmetric synthesis of anti-α-substituted β-amino ketones from sulfinimines

Previously unknown, enantiopure, β-amino ketones were prepared in modest yield by addition of lithium reagents to N-sulfinyl anti-α-substituted β-amino Weinreb amides. Grignard reagents failed to add to these Weinreb amides in contrast to the syn-α-substituted isomers which did. The anti-α-substituted β-amino Weinreb amides were prepared by addition of LiN(OMe)Me to the corresponding N-sulfinyl anti-α-substituted β-amino esters because α-alkylation of N-sulfinyl β-amino Weinreb amide enolates resulted in poor diastereoselectivities.