Tf2NH-catalyzed,highly regio-and stereo-selective synthesis of trisubstituted alkenes and indane derivatives from benzylic alcohols and alkenes

A reaction of benzylic alcohols with alkenes has been developed in the presence of bis(trifluoromethane)sulfonimide for the synthesis of trisubstituted alkenes and indane derivatives with high stereoselectivity.In general,benzylic alcohols react with 1,1-diaryl alkenes to afford trisubstituted alkenes,and the reaction with 1,2-disubstituted and trisubstituted alkenes affords indane derivatives through a [3 + 2] annulation reaction.     

A synthesis of trisubstituted alkenes by a Ru-catalyzed addition

Catalyzed by ruthenium trisacetonitrile hexafluorophosphate 4, the Alder-ene type reaction of alkenes and internal alkynes provides an effective way to synthesize trisubstituted alkenes. Unlike most typical olefination protocols, this reaction is atom economical, and affords trisubstituted alkenes with defined olefin geometry. The regioselectivity can be explained invoking a steric argument based on the proposed mechanism. The first C-C bond formation generally involves sterically less hindered carbons of the alkenes and alkynes. Modest to very high regioselectivity can be achieved depending on the steric difference of the two substituents of alkynes.     

A sequential highly stereoselective hydroboration and Suzuki-Miyaura cross-coupling reaction of fluoroalkylated internal acetylenes: a practical one-pot synthesis of fluoroalkylated trisubstituted alkenes

The one-pot synthesis of trisubstituted alkenes starting from fluoroalkylated internal alkynes was investigated. Hydroboration of the alkynes proceeded in a highly regio- and stereoselective manner to give the corresponding vinylboranes in excellent yields. Without isolation, treatment of the vinylboranes with various aryl halides under the Suzuki-Miyaura cross-coupling conditions gave the fluoroalkylated trisubstituted alkenes in high yields with complete retention of the olefinic geometry.     

A general and stereoselective method for synthesis of tri- and tetrasubstituted alkenes

A convenient, general and stereoselective synthesis of trisubstituted alkenes and tetrasubstituted alkenes containing a cyanide function as well as trisubstituted episulphides have been elaborated. Methodology described for the preparation of these compounds is based on the corresponding readily available selenophosphates 1 and thiophosphates 2.     

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.     

TBAF-mediated reactions of 1,1-dibromo-1-alkenes with thiols and amines and regioselective synthesis of 1,2-heterodisubstituted alkenes

An efficient synthesis of trisubstituted alkenes including 1,2-heterodisubstituted alkenes has been described. Reactions of thiols and amines with 1,1-dibromo-1-alkenes in the presence of TBAF·3H(2)O afford (Z)-2-bromovinyl sulfides and (Z)-2-bromovinyl amines regio- and stereoselectively. The reaction proceeds under catalyst-free conditions with high efficiency. The coupling reactions of the obtained products bearing bromine atoms with phenylacetylene and phenylboronic acid gave trisubstituted alkenes in good to excellent yields. Cross-coupling with various N, O, S, and P nucleophiles selectively generated 1,2-N,O, 1,2-N,S, 1,2-S,P, 1,2-S,S, and 1,2-S,O heterodisubstituted alkenes.     

A radical procedure for the anti-Markovnikov hydroazidation of alkenes

A one-pot procedure for the efficient hydroazidation of alkenes involving hydroboration with catecholborane followed by reaction with benzenesulfonyl azide in the presence of a radical initiator is described. The regioselectivity is controlled by the hydroboration step and corresponds in most cases to an anti-Markovnikov regioselectivity. This procedure is applicable to a wide range of alkenes and gives excellent results with 1,2-disubstituted and trisubstituted alkenes.     

Amination of the Baylis–Hillman Acetates in Ethanol

Baylis–Hillman acetates in EtOH were substituted by various nitrogen nucleophiles to give the corresponding trisubstituted alkenes in high yields.     

Phosphorus Chemistry. III Preparation of Vinyl Deuterated Trisubstituted Alkenes

A facile procedure for the preparation of vinyl deuterated trisubstituted alkenes via reduction of the corresponding (2-oxoalkyl)triphenyl-phosphonium halides with sodium borodeuteride is described.     

Julia-Kocienski Olefination in the Synthesis of Trisubstituted Alkenes: Recent Progress

Julia-Kocienski olefination, a coupling reaction between a carbonyl component and a sulfone partner, has emerged as a powerful synthetic tool in the preparation of several organic compounds. A number of interesting examples involving particularly the preparation of trisubstituted alkenes along with important observations regarding the stereoselectivity of those reactions have been recently reported. This reviewing work covers the literature for the period 2016–2022 and describes in a comprehensive way the progress and developments of Julia-Kocienski olefination application in the synthesis of trisubstituted alkenes which serve as precursors of natural products and their analogs as well of pharmaceutically interesting/biologically important compounds. Moreover, key methodology results dealing with the investigation of the optimum conditions and stereoselectivities and new modifications and approaches are discussed.     

On the stereospecific conversion of proximally-oxygenated trisubstituted vinyltriphenylstannanes into stereodefined trisubstituted alkenes

[reaction: see text] Allylically oxygenated vinyl alpha-triphenylstannanes such as 22 can be readily converted into vinyl iodides and thereafter stereodefined trisubstituted alkenes with retention of configuration.     

Bond angle versus torsional deformation in an overcrowded alkene: 9-(2,2,2-triphenylethylidene)fluorene

Competition between bond angle and torsional strain in sterically crowded alkenes generally causes twisting in tetrasubstituted alkenes, while most structurally characterized trisubstituted alkenes are planar. To investigate structural effects of steric repulsion between a planar aromatic ring and a vicinal triphenylmethyl (trityl) group, 9-(2,2,2-triphenylethylidene)fluorene (1 a) was synthesized by reaction of 9-bromomethylenefluorene with triphenylmethyllithium. For comparison with a less strained analogue, 9-ethylidenefluorene (1 b) was prepared by reaction of fluorenone with ethylmagnesium bromide. The X-ray crystal structures show that the difference between bond angles at the 9-fluorenyl carbon atom is much larger for 1 a (12.9 degrees) than 1 b (2.6 degrees). Bond angle and torsional deformations were compared theoretically (HF/6-31+G*) with the tert-butyl analogue (1 c), 1,2,2-tri-tert-butylethene (7), and 2,4,4-trimethyl-2-pentene (8) and crystallographically with six known 1,1-diaryl-2-tert-alkylethenes (2). The trisubstituted alkenes formed three groups with 1) large angle distortion with moderate twisting (1 a, 1 b, and 7), 2) moderate bending with a large range of torsional angles (2), and 3) little bending or twisting (1 b and 8). For the entire series, there appears to be a delicate balance between angle and torsional deformation, but twisting appears to produce smaller relief from steric strain than angle bending. In the crystallographically characterized trisubstituted alkenes, the choice between the two is mainly determined by more subtle packing forces.     

The palladium-catalyzed reaction of aryl iodides with mono and disubstituted acetylenes: a new synthesis of trisubstituted alkenes.

Mono and disubstituted acetylenes react with aryl iodides containing a variety of functional groups in the presence of palladium catalyst, formic acid and a tertiary amine to give trisubstituted alkenes.     

Diastereoselective remote C-H activation by hydroboration

Hydroboration of tetrasubstituted or trisubstituted alkenes with BH(3) and subsequent thermolysis allows remote diastereoselective C-H activation of neighboring aryl rings. Tetrasubstituted and trisubstituted 1,1-diphenylethylene derivatives undergo a highly stereoselective 1,2-rearrangement followed by remote C-H activation to lead, after oxidative workup, to a diol in which the relative stereochemistry of two stereocenters has been controlled. The mechanism of this remote activation has been studied and extended to related molecules that undergo this stereoselective C-H activation, namely alkenylbiphenyl systems or alkenes with only one phenyl ring, such as alkenylbenzenes, or bicyclic systems. We have shown that this reaction allows diastereoselective synthesis of molecules with up to three contiguous chiral centers.     

Vicinal C,H spin coupling constants in determining alkene stereochemistry

Further examples of the diagnostic vicinal C,H coupling constants of trisubstituted alkenes are reported, and the application of the method confirms the structures of four dimethyl acetylenedicarboxylate adducts.     

Solvent-free NbCl5 catalyzed condensation of 1,3-dicarbonyl compounds and aldehydes: a facile synthesis of trisubstituted alkenes

A simple preparation of trisubstituted alkenes by condensation of β-diketones or β-ketoesters with aldehydes in presence of NbCl₅ as a Lewis acid catalyst in solvent-free conditions is described.     

Silver sequestration of halides for the activation of Pd(OAc)2 catalyzed Mizoroki‐Heck reaction of 1,1 and 1,2 ‐ Disubstituted alkenes

A ligand free catalytic system consisting of Pd(OAc)₂ (cat) and stoichiometric quantities of silver salts, AgOAc or AgBF₄, exhibit high efficiency in the Mizoroki‐Heck arylation, transforming aryl iodides and 1,1 as well as 1,2 disubstituted alkenes into 1,1,2 – trisubstituted aryl alkenes in excellent yields in very short reaction times.     

Rhodium-catalyzed addition of arylboronic acids to alkynyl aza-heteroaromatic compounds in water

Alkynyl heteroaromatic compounds reacted with arylboronic acids to give addition products in the presence of a rhodium catalyst. The best results were obtained when a novel pyridine-substituted water-soluble phosphine ligand was used. The reactions proceed to give trisubstituted alkenes from various arylboronic acids and alkynyl heteroaromatic compounds with high regioselectivity. Only alkynes with a nitrogen atom in proximity to the triple bond were converted to the corresponding alkenes, as expected for a chelation-controlled addition.     

Ene-like addition of an oxoammonium cation to alkenes: highly selective route to allylic alkoxyamines

The oxoammonium cation of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate (1) adds rapidly at room temperature in an ene-like fashion to trisubstituted alkenes to afford allylic alkoxyamines in high yield. [reaction: see text]     

Metal-free oxidative cyclization of urea-tethered alkenes with hypervalent iodine

A metal-free oxidative cyclization of ureas onto unactivated alkenes using iodosylbenzene and an acid promoter is described. The products isolated are predominantly bicyclic isoureas resulting from an intramolecular oxyamination reaction. The acid type and urea substitution have a strong effect on the product formed. A variety of substrates form the isourea with high diastereoselectivity via syn addition including di- and trisubstituted alkenes. Hydrolysis of the isourea gives access to new diastereomerically pure prolinol derivatives.