An efficient multicomponent stereoselective synthesis of 1,2,4-trisubstituted 1,3-thiazetidines

The first one-pot three-component coupling reaction of O,O-diethyl hydrogen phosphorodithioate, aldehydes, and aldimines affording 1,2,4-trisubstituted 1,3-thiazetidines is reported. The product is obtained in moderate to high yields (45-94%) and has excellent diastereoselectivity (90-96%) in favour of the cis isomer. Shorter reaction times, ambient temperature, operational simplicity, and high yields are the salient features of the present procedure.     

Cyanamides in the synthesis of 1,3-thiazole and 1,3-thiazine derivatives

Hetaryl, aroyl, and aryl cyanamides react with 2-sulfanylbenzoic acid, 2-aminobenzenethiol, and 2-aminoethanethiol to give derivatives of 2-amino-4H-1,3-benzothiazin-4-one, 1,3-benzothiazol-2-amine, and 4,5-dihydro-1,3-thiazol-2-amine.     

Reactivity of digallane toward nitrogen-containing compounds

The reactions of [LGa–GaL] (L = dpp-bian = 1,2-bis[(2,6-di-isopropylphenyl)imino]acenaphthene) with ammonia and pyrrolidine in toluene lead to the formation of adducts [L(NH₃)Ga–Ga(NH₃)L], [L(HNC₄H₈)Ga–GaL] and [L(HNC₄H₈)Ga–Ga(HNC₄H₈)L], respectively. In contrast, the reaction between crystalline digallane and an excess of pyrrolidine leads to the formation of compound [LGa(NC₄H₈)(HNC₄H₈)]. The complex [LGa(C₅H₅N)(μ-O)Ga(C₅H₅N)L] was obtain from reaction of digallane with N₂O in the presence of pyridine.     

Synthesis,Structure, and Reactivity of Naphtho-Fused 2-(Furan-2-yl)-1,3-thiazole

The condensation of naphthalen-2-amine with furan-2-carbonyl chloride in propan-2-ol gave N-(naphthalen-2-yl)furan-2-carboxamide which was treated with excess P₂S₅ in anhydrous toluene to obtain the corresponding thioamide. The oxidation of the latter with potassium hexacyanoferrate(III) in alkaline medium afforded 2-(furan-2-yl)naphtho[2,1-d][1,3]thiazole. A probable mechanism of its formation was proposed, and the ring closure involving C¹ of the naphthalene fragment was substantiated by quantum chemical calculations. Electrophilic substitution reactions of 2-(furan-2-yl)naphtho[2,1-d][1,3]thiazole (nitration, bromination, formylation, and acylation) involved exclusively the 5-position of the furan ring.     

Task-specific ionic liquid-catalyzed efficient couplings of indoles with 1,3-dicarbonyl compounds: an efficient synthesis of 3-alkenylated indoles

Direct alkenylation of indoles at the 3-position with 1,3-dicarbonyl compounds under Brønsted acidic ionic liquid catalysis has been developed. The yields were excellent, and the catalyst can be reused at least six times without noticeable loss of catalytic activity.     

Reactivity of aromatic compounds toward diphenylcarbonyl oxide

The reactivity of organic compounds (PhH, PhMe, PhF, PhCl, PhOH, PhOEt, PhCHO, Ph₂CO, PhCN, Ph₂S, Ph₂SO, Ph₂SO₂, andp-Me₂C₆H₄) toward diphenylcarbonyl oxide Ph₂COO was characterized by thek ₃₃/k ₃₁ ratio, wherek ₃₃ andk ₃₁ are the rate constants for the reactions of Ph₂COO with the arene and diphenyldiazomethane Ph₂CN₂, respectively. The values ofk ₃₃/k ₃₁ vary from 2.6·10⁻³ (PhCN) to 0.65 (Ph₂S) (70°C, MeCN). The reaction is preceded by formation of a complex with charge transfer from a substrate to Ph₂COO. In the reactions with aromatic substances (except for Ph₂SO, PhCHO, and Ph₂CO), carbonyl oxide behaves as an electrophile. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2197–2201, November, 1998.     

Reactivity of Mitsunobu reagent toward carbonyl compounds

[reaction: see text] The nitrogen-based nucleophile generated from azodicarboxylate and triphenylphosphine displayed an excellent reactivity toward carbonyl compounds to generate a variety of different final products depending on the substituent pattern on the carbonyl carbon. From the structures of these adducts, a straightforward mechanistic interpretation for the formation of different products is provided.     

An efficient stereoselective synthesis of (+)-deoxoprosophylline

An efficient stereoselective synthesis of (+)-deoxoprosophylline from readily available p-anisaldehyde is described. Key steps in the synthesis include the stereoselective amination of anti-1,2-dibenzyl ether using chlorosulfonyl isocyanate, intermolecular olefination, and Pd-catalyzed intramolecular cyclization.     

Highly efficient and stereoselective synthesis of beta-glycolipids

beta-Galactosylceramide and glycolipid analogues were prepared in high yield and with complete chemo and stereoselectivity by reaction of alpha-iodo glycosides with stannyl ceramides, formed in situ. TBAI was used to activate both the iodogalactose and the stannyl ether.     

Boron-directed regio- and stereoselective enyne cross metathesis: efficient synthesis of vinyl boronate containing 1,3-dienes

[reaction: see text] Regio- and stereoselective enyne cross metathesis reactions between borylated alkynes and terminal alkenes were realized to provide a variety of functionalized vinyl boronates. High chemical yield and regioselectivity was achieved irrespective of substituents on the alkyne and alkene counterparts, whereas Z/E-selectivity was found to be dependent upon the substituents both on the alkyne and alkene.     

1,3-Dicarbonyl compounds in stereoselective domino and multicomponent reactions

Modern organic synthesis focuses on the discovery and the development of stereoselective multiple bond-forming transformations allowing the creation of several covalent bonds in a single operation. Hence, the number of steps required to obtain a target molecule is reduced, which nicely addresses the efficiency and economy criteria of ‘green chemistry’. In this context, 1,3-dicarbonyl compounds are exceptional synthetic platforms due to the presence of four contiguous reaction sites. This functional group density allows cascades of elemental steps from simple substrates leading to the selective formation of elaborated molecular architectures displaying a large functional diversity.     

Convergent stereoselective and efficient synthesis of furanic-steroid derivatives

The stereoselective synthesis of furanic-steroid derivatives involving ring-closing metathesis and catalytic hydrogenation as key steps is described. The synthetic strategy was first illustrated by the synthesis of the furanic-estrane derivative 1 in seven steps starting from estrone and 2-methylene-propane-1,3-diol. This compound initially targeted as a potential inhibitor of 17β-hydroxysteroid dehydrogenase type 1 by a docking experiment was found to inhibit the enzyme. The scope of this new strategy was also extended to furanic-androstane derivatives by synthesizing compound 20.     

Diacetoxyiodobenzene-mediated oxidative addition of 1,3-dicarbonyl compounds to olefins: an efficient one-pot synthesis of 2,3-dihydrofuran derivatives

A variety of olefins react with -dicarbonyl compounds at 0°C in the presence of diacetoxyiodobenzene to afford highly substituted 2,3-dihydrofuran derivatives in good to excellent yields.     

Highly stereoselective synthesis of 1,3-aminoalcohols via Mannich reactions

Diastereoselective synthesis of β-amino ketones by a one-pot Mannich reaction and their subsequent reduction afforded sterically congested enantiomerically pure 1,3-aminoalcohols in high diastereoselectivity: dr up to >98:<2 over two steps. The absolute configurations of the newly created stereogenic centers were assigned by NMR spectroscopy and chemical correlation.     

Totally stereoselective synthesis of 1,3-disaccharides through Diels-Alder reactions

A nonclassical, totally stereoselective synthesis of orthogonally protected 1,3-disaccharides is reported. Enantiomerically pure beta-keto-delta-lactones, efficiently obtained from glucal and galactal, are transformed into electron-poor heterodienes and chemo-, regio-, and stereoselectively cycloadded to glycals as electron-rich dienophiles, to directly afford 2-thiodisaccharides. The reductive desulfurization of the latter smoothly gave the corresponding 2,2'-dideoxydisaccharides.     

Electrolysis as an efficient key step in the homogeneous polymer-supported synthesis of N-substituted pyrroles

[reaction: see text]. An efficient and general route to the soluble polymer-assisted synthesis of a set of 14 different N-substituted pyrroles using dendritic polyglycerol as a high-loading support is presented. The transformation of furan to the key intermediate 2,5-dialkoxytetrahydrofuran was performed by electrochemical oxidation followed by catalytic hydrogenation with Pt/C in high yield. Both reactions required heterogeneous reagents which can be conveniently used with polyglycerol as a soluble support.     

Highly stereoselective and efficient total synthesis of (+)-laurencin

A highly stereoselective and efficient asymmetric total synthesis of (+)-laurencin (1) has been accomplished from the known oxazolidinone 5 in 15 steps. The route features an efficient internal alkylation to form oxocene 3 from 4 and a novel use of acetonitrile anion as a two-carbon acetaldehyde equivalent for direct synthesis of ketone 2 from alpha-alkoxy amide 3.