An Efficient One-pot Synthesis of β-Amino/β-Acetamido Carbonyl Compounds via ZrCl4-catalyzed Mannich-type Reaction

Zirconium(IV) chloride catalyzed efficient one-pot synthesis of β-amino/β-acetamido carbonyl compounds at room temperature is described. In the presence of ZrCl4, the three-component Mannich-type reaction via a variety of in situ generated aldimines, with various ketones, aromatic aldehydes and aromatic amines in ethanol, led to the formation of β-amino carbonyl compounds and the four-component Mannich-type reaction of aromatic aldehydes with various ketones, acetonitrile and acetyl chloride resulted in the corresponding β-acetamido carbonyl compounds in high to excellent yields. This methodology has also been applied towards the synthesis of dimeric β-amino/β-acetamido carbonyl compounds.     

Mechanistic Insights into the One‐Pot Synthesis of Propargylamines from Terminal Alkynes and Amines in Chlorinated Solvents Catalyzed by Gold Compounds and Nanoparticles

Propargylamines can be obtained from secondary amines and terminal alkynes in chlorinated solvents by a three‐ and two‐component synthesis catalyzed by gold compounds and nanoparticles (Au‐NP) under mild conditions. The use of dichloromethane allows for the activation of two C? Cl bonds and a clean transfer of the methylene fragment to the final product. The scope of the reaction as well as the influence of different gold(III) cycloaurated complexes and salts has been investigated. The involvement of gold nanoparticles generated in situ in the process is discussed and a plausible reaction mechanism is proposed on the basis of the data obtained.     

Stereoselective Total Synthesis of 4‐Ketoclonostachydiol

An efficient stereoselective total synthesis of the bioactive 14‐membered natural macrocyclic bislactone 4‐ketoclonostachydiol is described. The strategy involves a Jacobsen's hydrolytic kinetic resolution (HKR), epoxide opening, MacMillan α‐hydroxylation, Horner? Wadsworth? Emmons olefination, a Grignard reaction, and Hoveyda? Grubbs‐II‐catalyzed ring‐closing metathesis (RCM) as key steps.     

A One‐Pot Organometallic Route from a 4‐Alkenylpyridine to a 4,4‐Spiro‐Linked Ethyl 1,4‐Dihydropyridine‐1‐carboxylate

In a one‐pot process without isolation of intermediates, (but‐3‐en‐1‐yl)pyridine ( 13 ) is treated sequentially with dicyclohexylborane, trimethylaluminium, and ethyl carbonochloridate yielding ethyl 1,4‐dihydro‐4,4‐(tetramethylene)pyridine‐1‐carboxylate (=ethyl 8‐azaspiro[4.5]deca‐6,9‐diene‐8‐carboxylate; 2 ) in 46% yield based on starting alkenylpyridine 13 (Scheme 5).     

Synthese und Kristallstruktur eines μ-Methylen-μ-hydrido-dialanats [R2Al(μ-CH2)(μ-H)AlR2]− (R = CH(SiMe3)2)

Synthesis and Crystal Structure of a μ-Methylene-μ-hydrido-dialanate [R₂Al(μ-CH₂)(μ-H)AlR₂]^? (R = CH(SiMe₃)₂) tert-Butyl lithium reacts with the recently synthesized methylene bridged dialuminium compound [(Me₃Si)₂CH]₂Al? CH₂? Al[CH(SiMe₃)₂]₂ 2 in the presence of TMEDA under β-elimination; the thereby formed hydride anion is bound in a chelating manner by both unsaturated aluminium atoms forming a 3c–2e–Al? H? Al bond. The crystal structure of the product shows two independent molecules differing only slightly in bond lengths and angles, but significantly in conformation. While one of the Al₂CH heterocycles deviates little from planarity with a rough C₂ symmetry for the whole anion, the other one is folded with an angle of 21.1° and the arrangement of the substituents is best described by C_s symmetry.     

Facile One‐Pot Multicomponent Synthesis of β‐Acetamido Ketones with Amberlyst‐15 as Heterogeneous Catalyst

The one‐pot multicomponent coupling of an aromatic aldehyde, an enolizable ketone or keto ester, acetonitrile, and acetyl chloride at room temperature in the presence of Amberlyst‐15 as catalyst affords β‐acetamido ketones in high yields. The inexpensive catalyst works under heterogeneous conditions and can be readily reused.     

Efficient Synthesis of β‐Acetamido Ketones and Esters Using Aluminum Chloride as an Inexpensive and Green Catalyst

Aluminum chloride (AlCl₃) efficiently catalyzes one‐pot multicomponent condensation of enolizable ketones or alkyl acetoacetates with aldehydes, acetonitrile and acetyl chloride to afford β‐acetamido ketone or ester derivatives in high to excellent yields and in relatively short reaction times. Moreover, by this synthetic method, some novel β‐acetamido ketones and esters (i.e. one complex structure) are prepared.     

Transition‐Metal‐Free Formal Sonogashira Coupling and α‐Carbonyl Arylation Reactions

Transition‐metal‐free formal Sonogashira coupling and α‐carbonyl arylation reactions have been developed. These transformations are based on the nucleophilic aromatic substitution (S_NAr) of β‐carbonyl sulfones to electron‐deficient aryl fluorides, producing a key intermediate that, depending on the reaction conditions, gives the aromatic alkynes or α‐aryl carbonyl compounds. The development of these reactions is presented and, based on investigations under basic and acidic conditions, mechanisms have been proposed. To develop the formal Sonogashira coupling further, a milder, two‐step protocol is also disclosed that expands the reaction concept. The scope of these reactions is demonstrated for the synthesis of Sonogashira and α‐carbonyl arylated products from a range of electron‐deficient aryl fluorides with a variety of functional groups and aryl‐, heteroaryl‐, alkyl‐, and alkoxy‐substituted sulfone nucleophiles. These transition‐metal‐free reactions complement the metal‐catalyzed versions in terms of substitution patterns, simplicity, and reaction conditions.     

A Functionalized Spiro[chlorin‐porphyrin]‐Type ‘Dimer’ Dizinc Complex from Rapid [4+2] Self‐cycloaddition of a Conjugated [β,β′‐Bis(methylene)porphyrinato]zinc

Thermal extrusion of SO₂ from β,β′‐sulfolenoporphyrins is an effective method for in situ generation of β,β′‐bis(methylene)porphyrin which remained unobserved in typical synthetic applications but underwent quickly efficient [4+2]‐cycloaddition reactions with dienophiles.We now report the thermal extrusion of SO₂ from the symmetrical (tetra‐β,β′‐sulfolenoporphyrinato)zinc 1?Zn in the absence of a dienophile (Scheme). In the event, the thermally in situ generated conjugated diene underwent a [4+2] self‐cycloaddition, to give the {spirobi[tri‐β,β′‐sulfolenoporphyrinato]}dizinc 4?2Zn . This chiral (racemic) spirobiporphyrinoid dizinc complex represents the combination of the closely positioned and interacting chromophores of a (porphyrinato)zinc and of a (β‐methylene‐β,β′‐dihydroporphyrinato)zinc. It carries six sulfoleno moieties that are still available for further SO₂ extrusion and cycloaddition reactions.     

Palladium‐Catalyzed Insertion of α‐Diazoesters into Vinyl Halides To Generate α,β‐Unsaturated γ‐Amino Esters

As easy as 1, 2, 3 : A palladium‐catalyzed three‐component coupling generates α,β‐unsaturated γ‐amino acids in a single step (see scheme). The reaction is believed to involve migration of a vinyl substituent to a highly electrophilic palladium carbene. Unlike previous synthetic approaches, this synthesis provides access to γ‐amino acids with non‐natural side chains.

     

Asymmetric Photochemical Synthesis of Chiral 5‐(R)‐(l)‐Menthyloxy‐4‐Cycloaminobutyrolactones

Through photocatalysed regiospecific and stereoselective additions of cycloamines to 5‐(R)‐(l)‐menthyloxy‐2 (5H)‐furanone (3), chiral 5‐(R)‐(l)‐menthyloxy‐4‐cycloaminobutyrolactones were synthesized. In the new asymmetric photoaddition of compound 3, the N‐methyl cyclic amines (4) gave novel chiral C? C photoadducts (5) in 24–50% isolated yields with d. e. ≥ 98%. However, the secondary cyclic amines (6) afforded optically active N? C photoadducts (7) in 34–58% isolated yields with d. e. ≥ 98% under the same condition. All the synthesized optically active compounds were identified on the basis of their analytical data and spectroscopic data, such as [α]₅₈₉²⁰, IR, ¹H NMR, ¹³C NMR, MS and elementary analysis. The photosynthesis of chiral butyrolactones and its mechanism were discussed in detail.