Synthesis of β-Amino-α,α-dichloro Sulfones from Vinyl Sulfones

β-amino-α,α-dichloro sulfones 3 are prepared by the reaction of vinyl sulfone 1 with primary or secondary amines 2in the presence of CCI₄ and NaH.     

Synthetic Applications of π-Electron-Deficient Sulfones

Abstract

The use of π-electron-deficient aryl sulfones, especially 3,5-bis(trifluoromethyl) phenyl alkyl sulfones (BTFP-sulfones) as soft nucleophiles, as caboxylic acid protecting group and in Julia–Kocienski olefination reactions is described. In the case of α-(arylsulfonyl)acetates dialkylation, reactions are performed under phase-transfer analysis (PTC) conditions using K ₂ CO ₃ as base. Esters derived from 2-(arylsulfonyl)ethanol can be deprotected using aqueous NaHCO ₃ . Alkyl BTFP sulfones are coupled with carbonyl compounds using KOH or P4-t-Bu as bases to give the corresponding alkenes after Smiles rearrangement.     

Alkatrienyl Sulfoxides and Sulfones,VIII: Diels–Alder Reaction of 3‐Methylpenta‐1,2,4‐trienyl Phenyl Sulfoxide with Maleic Anhydride

Regio‐and stereo‐selective Diels–Alder reaction of 3‐methylpenta‐1,2,4‐trienyl phenyl sulfoxide with maleic anhydride in the absence or presence of a Lewis acid as catalyst with formation of sulfinyl‐substituted benzofuran or norbornene cycloadducts, respectively, is described.     

One-Pot Stereoselective Synthesis of (Z)-1,2-Disubstituted Vinyl Sulfones by Hydrostannylation–Stille Tandem Reaction of Acetylenic Sulfones

(Z)-1,2-Disubstituted vinyl sulfones can be stereoselectively synthesized in one pot under mild conditions, in good yields, by the palladium-catalyzed hydrostannylation of acetylenic sulfones with tributyltin hydride, followed by Stille coupling with aryl iodides.     

Solid-phase Synthesis of Vinyl Sulfones Using Polystyrene-supported Selenomethyl Phenyl Sulfone

The solid-phase preparation of vinyl sulfones via a novel polystyrene-supported selenomethyl phenyl sulfone reagent has been reported.     

An Efficient Synthesis of Derivatives of 2‐Acetamido‐4‐amino‐2,4,6‐trideoxy‐D‐galactopyranose

Abstract

Methyl 2‐acetamido‐4‐amino‐2,4,6‐trideoxy‐α‐D‐galactopyranoside (10) was synthesized from D‐glucosamine hydrochloride in eight steps in an overall yield of 31%. Key steps include the selective benzoylation at O‐3 of methyl 2‐acetamido‐2,6‐dideoxy‐α‐D‐glucopyranoside in 89% yield and the subsequent Mitsunobu reaction using diphenylphosphoryl azide as the azide source which proceeded in 92% yield. Di‐ and mono‐benzyloxycarbonyl derivatives of 10 were also prepared.     

Preparation of Some Derivatives of N‐tert‐Butyldecahydro‐3‐isoquinoline Carboxamide

N‐tert‐Butyldecahydro‐3‐isoquinoline carboxamide (1) is a key structural fragment present in a variety of medicinally important HIV protease inhibitors. Derivatives of this carboxamide were prepared by alkylation with either 2‐iodoethanol, allyl bromide, or bromoacetaldehyde dimethylacetal. The corresponding aldehyde of the dimethylacetal derivative was prepared by reaction with BBr₃ in CH₂Cl₂.     

Preparation of Alkyl Carbamate of 1‐Protected Indole‐3‐methylamine as a Precursor of Indole‐3‐methylamine

A series of alkyl carbamates 3 of 1‐protected indole‐3‐methylamines, alkyl carbamates 6 of thiophenylmethylamines, and pyrrolylmethylamines were prepared from the corresponding acetamides 2 and 5 in good to excellent yields via diacetoxyiodobenzene‐promoted Hofmann rearrangement. For a successful Hofmann rearrangement, an electron‐withdrawing group on position 1 of indolylacetamide and pyrrolylacetamide was required. The alkyl carbamate 3g was demonstrated to serve well as a stable precursor of 1‐protected indole‐3‐methylamine 1.     

One‐Pot Synthesis of Ene‐Lactams via N‐Debenzylation of Keto‐Containing N‐2,4‐Dimethoxylbenzylamides

Abstract

A general method of ene‐lactam preparation is described. Ene‐lactams can be prepared efficiently from keto‐containing N‐2,4‐dimethoxylbenzylamides in good to excellent yields. This method is applicable for the preparation of substituted δ‐, γ‐, and ?‐ene‐lactams and bicyclic ene‐lactams.     

Synthesis of 2,3‐Dihydroxy‐1‐Epilupinine

The 1,3‐dipolar cycloaddition of unsaturated D‐threo‐hexaldonolactone 3 and a six‐membered cyclic nitrone 11 led to a single adduct 15, which could be transformed into (1S, 2S, 3S, 9aS)‐2,3‐dihydroxy‐1‐hydroxymethyl‐quinolizidine 28 related to epilupinine via a reaction sequence involving rearrangement of the six‐membered lactone ring into a five‐membered one, removal of the terminal carbon atom from the sugar chain, cleavage of the N‐O bond, and the intramolecular alkylation of the nitrogen atom.      

Bromination of 4‐Dichloromethyl‐4‐methylcyclohexa‐2,5‐dien‐1‐ones

Bromination of 4‐dichloromethyl‐4‐methylcyclohexa‐2,5‐dien‐1‐one and 4‐dichloromethyl‐3,4‐dimethylcyclohexa‐2,5‐dien‐1‐one has been studied. The reaction conditions required for the formation of mono‐, di‐, and tribrominated products have been optimized.     

Synthesis of O‐β‐D‐Glucopyranosides of 7‐Hydroxy‐3‐(imidazol‐2‐yl)‐4H‐chromen‐4‐ones

The 7‐hydroxy‐3‐formyl‐4H‐chromen‐4‐one 1 reacted with various cyclic 1,2‐dicarbonyl compounds in the presence of ammonium acetate to furnish 7‐hydroxy‐3‐([4,5‐fused] imidazol‐2‐yl)‐4H‐chromen‐4‐ones 2a–f, which on glucosylation with α‐acetobromoglucose affords 2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyloxy‐3‐([4,5‐fused] imidazol‐2‐yl)‐4H‐chromen‐4‐ones 3a–f. 7‐O‐β‐D‐Glucopyranosyloxy‐3‐([4,5‐fused] imidazol‐2‐yl)‐4H‐chromen‐4‐ones 4a–f were prepared by deacetylation with anhydrous zinc acetate in absolute methanol. The structure of these new O‐β‐D‐glucosides was established on the basis of chemical, elemental, and spectral analysis. These compounds were evaluated for their in vitro biological activity.

     

Heterocyclization of Imidates with 3‐Alkyl‐5‐amino‐1‐phenyl‐1,2,4‐triazoles: Synthesis of New Triazolotriazines

Some novel triazolo[4,3‐a]triazines derivatives were synthesized by reaction of N‐cyanoimidates and N‐ethoxycarbonylimidates with 3‐alkyl‐5‐amino‐1‐phenyl‐1,2,4‐triazoles.     

Application of Dichlorovinyl Xyloside for the Novel Synthesis of 2,3,4‐Tri‐O‐methyl‐D‐xylono‐1,5‐lactone

A novel synthesis of 2,3,4‐tri‐O‐methyl‐D‐xylopyranose, 4, and its oxidation product 2,3,4‐tri‐O‐methyl‐D‐xylono‐1,5‐lactone, 5, are reported. The new synthesis applies a regioselective Wittig‐like reaction of tetra-O-acetyl-D-xylopyranase, 1, with triphenylphosphine and carbon tetrachloride to yield an O‐dichlorovinyl xyloside protected at C‐1, 2. The protecting group facilitates the permethylation of xylose and is removed under the methylation conditions, to yield tetra-O-acetyl-D-xylopyranase, 3. The anomeric methyl group was removed under mildly acidic conditions to give 2,3,4‐tri‐O‐methyl‐D‐xylopyranose, 4, in good yield. Compound 4 was oxidized using pyridinium chlorochromate to give the title compound, 5, in 95% yield.     

Structure of 2,4,4,5,5‐pentamethyl‐2‐imidazoline‐1‐oxyl‐3‐oxide

The crystal and molecular structures of the stable nitroxide radical 2,4,4,5,5pentamethyl2imidazoline1oxyl3oxide was determined. The N—O bond lengths are 1.279(2) and 1.280(2), respectively. The O^-—N⁺=C—N— O fragment is nearly planar with carbon atoms of the ethyl fragment that deviated from the O—N⁺=C—N—O plane by –0.204(5) and +0.176(5). The minimum intermolecular distance between the oxygen atoms of NO groups is 4.094.     

Radical Addition Reactions of α-Substituted β,β-Difluorovinyl Sulfones

The radical addition reactions of α-substituted β,β-difluorovinyl sulfones 1 with α-oxy and acyl radical species, such as 1,3-dioxolane, tetrahydrofuran, 1,4-dioxane, butanal and hexanal, afforded radical addition products 2--16 in good yields.     

Synthesis of cis‐3‐methyl‐4‐aminopiperidine Derivatives

A facile approach for the preparation of cis‐3‐methyl‐4‐aminopiperidine derivatives is described. The synthesis was carried out via regioselective ring opening of N‐benzyl‐3‐methyl‐3,4‐epoxi‐piperidine (8), which can be easily obtained in two steps from the corresponding N‐benzyl‐pyridinium salt (5). Seven new cis‐3‐methyl‐4‐amino and amido piperidines compounds were obtained.     

Facile Synthesis of 3,3‐Dialkyl‐6‐phenyl‐imidazopyridinones

A series of novel 3,3‐dialkylated imidazopyridinones bearing 6‐aryl groups were designed as mimetics of active progesterone antagonists, 3,3‐disubstituted‐5‐arylindoles. The four‐step synthetic route is described. The key steps are base‐catalyzed cyclization, base‐catalyzed alkylation, and Suzuki coupling reaction.     

Facile Synthesis of 2‐Alkylthio‐5,5‐dimethyl‐4H‐imidazol‐4‐ones

The isothiocyanate 3, obtained from aza‐Wittig reaction of iminophosphorane 2 with CS₂, reacts with phenylhydrazine to give thiosemicarbazide 4. Reactions of 4 with alkyl halides in the presence of K₂CO₃ directly provided 2‐alkylthio‐4H‐imidazol‐4‐ones 6 in good yields.