AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Depending on the kind of R1 and R2, cyclic carbonates 1, in the presence of 10 mol% of Pd(PPh3)4 and 10 equiv of paraformaldehyde, selectively undergo three types of reaction: 1 (R1, R2 ≠ H) give dienes 3 exclusively; 1 (R1 = R2 = H and R1 ≠ H, R2 = H) furnish 6-vinyl-1,3-dioxanes 5 exclusively, while 1 (R1 = H, R2 ≠ H) give rise to 4-pentenyl formates 4 selectively (together with 3 as the minor products).

Mit ausgezeichneten Diastereoselektivitäten lassen sich cyclische vinylsubstituierte Carbonate in ungesättigte offenkettige Carbonylverbindungen umwandeln [G1. (1)]. Maßgeblich für den Erfolg dieser Ringöffnung ist ein Pdo‐Komplex als Katalysator. Cn = komplex, auch cyclisch substituierte Kohlenstoffkette mit n = 0, 1, 2, 4, 8; R, R′ = H, Me.magnified image

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Both the C=S and C=C functionalities of N-arylmonothiomaleimides readily undergo a [4 + 2] cycloaddition reaction at ambient temperatures with both electron-donating and -withdrawing dienes, The C=S groups of N-arylmonothiomaleimides are generally more reactive than the C=C groups, especially toward dienes bearing conjugation and electron-attracting groups, and provide mixtures of ortho,endo products 3 and ortho,exo products 4 with complete regioselectivity (100% ortho) and with high stereoselectivity (more than 86% endo). The C=C groups, on the other hand, display a high stereoselectivity (100% endo) but a low regioselectivity, providing ortho,endo adducts 5 and meta,endo adducts 6 in ratios ranging from 1:1 to 6:1. Compared with N-phenylmono thiomaleimide ( 1), N-p-nitrophenylmonothiomaleimide (11a) is more reactive and displays a higher C=S vs. C=C chemoselectivity in favor of C=S, while N-p-anisyl (11b) and N-benzyl (11c) derivatives display quite the reverse reactivity and selectivity. N-Phenylmonothiocitraconimide (11d) serves as a C=S specific dienophile and reacts with dienes to furnish ortho,endo adducts 12 with excellent regio- and stereoselectivities (100% ortho,endo). Both hard (BF3.OEt2, TiCl4) and soft (CuBr.SMe2) Lewis acids enhance the reaction rate enormously and increase chemoselectivity in favor of C=S. The chemo- (C=S/C=C), regio- (ortho/metal) and stereochemical outcomes (endo/exo) are rationalized by transition structure analysis based on AM1 calculation.

Pd(II)-catalyzed intramolecular aminocarbonylation of olefins bearing many types of nitrogen nucleophiles has been examined under two typical conditions: acidic conditions [conditions A, typically PdCl(2) (0.1 equiv) and CuCl(2) (3.0 equiv) under 1 atm of CO at room temperature in methanol] and buffered conditions [conditions B, typically PdCl(2) (0.1 equiv) and CuCl(2) (2.3 equiv) under 1 atm of CO at 30 degrees C in trimethyl orthoacetate]. Among nitrogen nucleophiles, endo-carbamates 7 display distinctive reactivity: endo-carbamates 7a-k smoothly undergo intramolecular aminocarbonylation under conditions B to furnish 4-[(methoxycarbonyl)methyl]-2-oxazolidinones 8a-k in good yields, while they would not undergo the expected reaction under conditions A. Other nitrogen nucleophiles (exo-ureas 1, endo-ureas 3, exo-carbamates 5, and exo-tosylamides 9), on the other hand, satisfactorily undergo aminocarbonylation only under conditions A to give rise to 2, 4, 6, and 10, respectively, in good yields. Under conditions B, they are unreactive and provide either the expected products in poor yields or intractable mixtures of products. On the basis of this contrasting reactivity between endo-carbamates and other nitrogen nucleophiles, the chemoselective aminocarbonylation of 7l-o has been achieved; aminocarbonylation takes place at the endo-carbamate moieties to furnish 8l-o exclusively under conditions B, and aminocarbonylation occurs at the exo-carbamate, exo-urea, and exo-tosylamide moieties to yield 13a-d exclusively under conditions A.

The Wacker-type aminocarbonylation of unsaturated amides shows distinctive dependence of reactivity on the reaction medium: endo nitrogen nucleophiles (endo-carbanates3 and -ureas 5) undergo aminocarbonylation either in neat methyl orthoacetate (MOA) or in methanol containing AcONa and MOA, while exo nitrogen nucleophiles (exo-carbamates1a, -ureas 1b, and -sulfonamides 1c) in methanol (cat. PdCl2, stoichiometric CuCl2 under 1 atm of CO). The generality is indicated by the chemoselective transformations of 7a-d either into 8a-d in MOA or into 9a-d in methanol.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

By the catalysis of palladium(0), S-allyl thiocarbamates 1 react with aryl iodides and vinyl bromides to give allyl aryl sulfides and allyl vinyl sulfides, respectively, in good yields.

AbstractThe iodoetherification of N‐substituted 3‐amino‐4‐penten‐1‐ol (1) [I2 and NaHCO3 (2 equivalents each) in ether/H2O at 0°C], providin the mixtures of N‐substituted cis‐ and trans‐ 3‐amino‐2‐iodomethyltetrahydrofurans (9), displayed diastereoselectivity which was found to correlate with the Taft σ* constants of the N‐substitutents (SO2CF3, SO2Me, SO2‐P‐Tol, COPh, COMe): log(cis‐9/trans‐9) = 0.616σ* – 1.67 (r = 0.997). the 2‐methyl‐substituted derivatives of 1 exhibit larger ρ values, while for the 4‐methyl derivative of 1 is approximately zero, Iodoetherification of a variety of N‐tosyl (σ* = 3.32) 1‐ and 2‐substituted derivatives of 1 afforded the corresponding cis isomers with 70 – >95% selectivities, while that of the N‐benzoyl (σ* = 2.20) derivatives furnished the trans isomeres with 70–80% selectivities. These results are interpreted in terms of a πC(4)–C(5)‐σ*C(3)–N interaction of conformer II. The N‐CO2R (R = Et, t‐Bu) and N‐SO2NMe2 derivatives of 1 display anomalously high cis selectivities.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Pd2+-catalyzed aminocarbonylation of O-2,3-butadienyl 1 and O-3,4-pentadienyl carbamates 5 stereoselectively provides 4-(1-methoxycarbonylviny])-1,3-oxazolidin-2-ones 2 and 4-(1-methoxy-carbonylvinyl)-1,3-oxazin-2-ones 6, respectively, in high yields.

The transformation of cyclic carbonates 1 to cyclic carbamates 4 is achieved in the presence of aryl or sulfonyl isocyanate by the catalysis of Pd(0) in high yield and with high structural flexibility. The reaction shows unique stereoselectivity: 3,4-disubstituted carbonates 2, irrespective of the composition of their stereoisomers, provide trans-5 exclusively or predominantly over cis-5. Mixtures of cis- and trans-3,5-disubstituted carbonates 3 furnish either cis-6 or trans-6 in high selectivity depending on the reaction conditions (kinetic or thermodynamic control, respectively). H-1 NMR and X-ray structure analyses of 5 and 6 indicate that the stereochemical outcome is governed by an A1,2-strain between N-sulfonyl and C5-vinyl substituents.

2-Hydroxybut-3-enylamines 1 undergo a novel Pdl-catalysed 5-endo-trigonal cyclization to provide pyrrolines 2, pyrroles 3, and/or 3-oxopyrrolidines 4 in good to moderate combined isolated yields; the hydroxy group is essential fbr the cyclization.

The thiocarbonyl group of monothiomaleimide 1 serves as a more reactive dienophile than the electron-deficient C=C double bond in the same molecule for the Diets-Alder reaction with dienes 2c-g and provides ortho-endo products 3 exclusively or predominantly over the other possible adducts 4-10.

The selectivity of iodoetherification of N-substituted 3-aminopent-4-en-1-ols 1, providing mixtures of N-substituted (E)- and (E)-3-amino-2-iodomethyltetrahydrofurans [(Z)-2 and (E)-2], correlates well with the electronic effects of the N-substituents, increasing with an increase in the electron withdrawing effect of the substituents.