Synthesis of amidinoformic acids using benzyl cyanoformate as a synthon

An efficient synthesis of a variety of $\text{N}$-substituted or $\text{N}$-unsubstituted amidinoformic acids was developed starting with benzyl cyanoformate.     

Regioselective synthesis of 5-unsubstituted benzyl pyrrole-2-carboxylates from benzyl isocyanoacetate

A general synthesis of 5-unsubstituted benzyl pyrrole-2-carboxylates was developed based on the reaction of β-nitroacetates with benzyl isocyanoacetate. The advantage of this route over other pyrrole syntheses was the regiochemical control of the substitution pattern on the pyrrole ring.     

Regioselective synthesis of 1,7-dioxaspiro[4.4]nonanes from a trimethylenemethane dianion synthon

2-Chloromethyl-3-(2-methoxyethoxy)prop-1-ene behaves as a versatile trimethylenemethane dianion synthon, precursor of a variety of methylidenic diols obtained by DTBB-catalysed lithiation in the presence of a carbonyl compound (E¹=R¹R²CO) in THF at −78 to 0 °C, followed by the addition of an epoxide [E²=R³R⁴C(O)CHR⁵] at 0 to 20 °C and final hydrolysis. These diols undergo double intramolecular iodoetherification in the presence of iodine and silver(I) oxide in THF or dioxane-water, to give the corresponding 1,7-dioxaspiro[4.4]nonanes, which can be easily oxidised to a variety of 1,7-dioxaspiro[4.4]nonan-6-ones. These skeletons are present in a wide series of natural products.     

Ketones as a new synthon for quinoxaline synthesis

o-Phenylenediamines react with an array of ketones in PEG-400 at 60 °C under an atmosphere of air in the presence of KOH to afford the corresponding quinoxalines in good yields.     

2-Carbomethoxycyclopentenone as a synthon. synthesis of sarkomycin

The first regiospecific synthesis of sarkomycin (II), a compound active against ascites-type tumors, is reported. Treatment of 2-carbomythoxycyclopentenone (I) with Et₂AlCN generated the carbon skeleton; aelective functional group manipulations then gave the keto lactone X and the protected hydroxy acid XI; and mild acid treatment of these led to sarkomycin.     

Design and synthesis of novel fused heterocycles using 4-chromanone as synthon

A new series of heterocyclic systems, including azole, azolopyrimidine, and pyridopyrimidine derivatives, attached to 2H-chromene scaffold, was prepared by a convenient procedure through the reactions of (E)-2-dimethylamino-methylene chromanone with different nitrogen binucleophiles. Various substituted chromeno[4,3-b]pyridine derivatives were also prepared through the reactions of (E)-2-dimethylaminomethylene chromanone with a series of active methylene compounds.

     

Regioselective lithiation of aryl benzyl ethers

The lithiation of a series of aryl benzyl ethers containing -F and -OMe groups has been studied. It was found that the presence of one or two fluorine atoms in the meta position relative to the oxygen atom prevents the lithiation at the benzyl carbon atom. 3-(3′,5′-Dimethoxybenzyloxy)fluorobenzene was lithiated and next reacted with DMF to give 2-(3′,5′-dimethoxybenzyloxy)-6-fluorobenzaldehyde. A three-step procedure was applied to remove three hydrogen atoms from 1,3-difluoro-5-(3′,5′-dimethoxybenzyloxy)benzene and replace them with methyl groups by reactions of the lithiated compounds with MeI.     

Regioselective synthesis of unsymmetrical C-aryl glycosides using silicon tethers as disposable linkers

Silicon tethers were employed to control the regiochemistry of Diels-Alder reactions between substituted benzynes and glycosyl furans as a key step in the syntheses of unsymmetrical representatives of three major groups of C-aryl glycosides. The cycloaddition precursors were readily prepared by O-alkylation of substituted phenols with various sugar-substituted furylsilane derivatives. Selective deprotonation on the benzene ring of these ethers led to a benzyne that underwent an intramolecular Diels-Alder reaction to give bridged cycloadducts. Fluoride-induced removal of the silicon tether and acid-catalyzed ring opening of the oxabicycloheptadiene subunit yielded the desired C-aryl glycosides as single isomers.     

Radical hydroxymethylation of alkyl iodides using formaldehyde as a C1 synthon

Radical hydroxymethylation using formaldehyde as a C1 synthon is challenging due to the reversible and endothermic nature of the addition process. Here we report a strategy that couples alkyl iodide building blocks with formaldehyde through the use of photocatalysis and a phosphine additive. Halogen-atom transfer (XAT) from α-aminoalkyl radicals is leveraged to convert the iodide into the corresponding open-shell species, while its following addition to formaldehyde is rendered irreversible by trapping the transient O-radical with PPh₃. This event delivers a phosphoranyl radical that re-generates the alkyl radical and provides the hydroxymethylated product.

Halogen-atom transfer (XAT) based on phosphoranyl radical chemistry enables the hydroxymethylation of alkyl iodides with formaldehyde.     

DMSO作为新的合成子在有机合成中的应用研究进展

二甲亚砜(DMSO)不但可以作为有机溶剂,同时还可以作为反应试剂,在有机合成中得到了广泛的应用.由于其具有来源广、价格低廉、操作简单等优点,近年来将DMSO作为反应试剂应用于有机合成反应引起了广大化学家的关注.本文作者对近几年来DMSO作为合成子在有机合成中的应用按照引入官能团的种类进行了总结,详细阐述了其转化为甲磺酰基、甲酰基、氰基、甲硫基等官能团的方法学研究,以期为开发DMSO新的应用提供参考依据.     

A novel synthesis of amino-1,2-oxazinones as a versatile synthon for beta-amino acid derivatives

The radical addition-cyclisation of alpha, beta-unsaturated hydroxamates containing an oxime ether provides a novel method for the stereoselective synthesis of amino-1,2-oxazinones. Its synthetic utility is demonstrated by a stereoselective synthesis of beta-amino acid derivatives, such as alpha-alkyl-beta-amino-gamma-lactone and alpha,beta-disubstituted beta-lactam.     

Recent advances in organic synthesis with CO2 as C1 synthon

Carbon dioxide as a green, nontoxic and low-cost C1 synthon holds great potential in organic synthesis. In this paper, the recent studies of conversion of CO₂ with organic compounds (including alkenes, alkynes, amines, allylamines, propenyl ketones, propargylic alcohols/amines, arenes, and heteroarenes as well as their derivatives) to value-added chemicals are briefly reviewed.     

Soluble poly(diacetylene)s using the perfluorophenyl-phenyl motif as a supramolecular synthon

A series of diacetylene monomers with benzoyl, 4-hexylbenzoyl, 4-dodecylbenzoyl, and perfluorobenzoyl substituents were synthesized and investigated with respect to their crystal structures and polymerizability. In the absence of perfluorophenyl-phenyl interactions, the crystal structures of related alkylated and nonalkylated derivatives were substantially different and dominated by the phase segregation between the alkylated side chains and the diaryl-substituted diacetylene cores. By contrast, the perfluorophenyl-phenyl interactions served as a reliable supramolecular synthon in that they persisted in the crystal structures of different alkylated and nonalkylated derivatives. The packing of the diacetylene functions was appropriate for a topochemical polymerization in these cases, and the perfluorophenyl-phenyl interaction determined the polymerization direction. As a result, soluble alternating diacetylene copolymers were obtained which were further characterized with solution phase methods.     

Copper-catalyzed cyanation of arenes using benzyl nitrile as a cyanide anion surrogate

The copper-catalyzed cyanation of arenes using benzyl nitrile as a cyanide anion surrogate furnishes aromatic nitriles in moderate to good yields. The cascade process involves a copper-catalyzed aerobic C-H oxidation, a retro-cyanohydrination, and a copper-catalyzed aerobic oxidative C-H functionalization.     

Radical-mediated diastereoselective construction of a chiral synthon for synthesis of dolabellanes

[reaction: see text] A useful trans-substituted multifunctional cyclopentane with a chiral quaternary center was selectively synthesized by free radical Michael addition to the (Z)-propionate or -malonate derivatives. The stereoselectivity could be reversed by changing the configuration of the double bond.     

Facile, stereoselective synthesis of (24R)-24,25-dihydroxyvitamin D3 using D-glyceric acid as a chiral synthon

A facile, stereoselective, and efficient synthesis of (24R)-24,25-dihydroxyvitamin D₃, using D-glyceric acid as a chiral synthon to construct the side chain and ergosterol as a precursor of the secosteroid skeleton, is described.     

Formal synthesis of (±)-camptothecin via tricyclic lactone as key synthon

Formal synthesis of (±)-camptothecin via CDE tricyclic lactone employing tandem Michael addition, Dieckmann condensation and addition-elimination reaction as key steps starting from glycinate is described.     

Etherification of benzyl alcohol under microwave irradiation using a heteropoly acid as catalyst

Selective dehydration of benzyl alcohol to dibenzyl ether using heteropoly acid as catalyst in solvent-free conditions under microwave irradiation has been studied. The microwave power and irradiation time, and concentration of heteropoly acid are key factors, and under the severe conditions dibenzyl ether was polymerized. This revised version was published online in August 2006 with corrections to the Cover Date.