Silafunctional compounds in organic synthesis. 27. (Isopropoxydimethylsilyl)methyl grignard reagent: A new nucleophilic hydroxymethylating agent for aldehydes and ketones

Nucleophilic hydroxymethylation of aldehydes and ketones has been achieved by the reaction with the (isopropoxydimethylsilyl)methyl Grignard reagent and the subsequent oxidative cleavage of the carbon-silicon bond.     

Methyl-triisopropoxy-titanium,a highly selective nucleophilic methylating reagent. Preliminary Communication

Replacement of lithium or magnesium by titanium can furnish nucleophilic organometallic reagents of high selectivity as exemplified by the title compound 1 (see Tables 1–3).     

Benzoylnitrene radical anion: A new reagent for the generation of M-2H anions

Benzoylnitrene radical anion, formed in high abundance by electron ionization of benzoylazide, is found to be a useful reagent for the formation of ionized reactive intermediates, such as diradicals and carbenes. The reactivity of the ion is similar to what is observed with atomic oxygen anion, occurring in many instances by H(2)(+) transfer. However, because benzoylnitrene radical anion is less basic than oxygen anion, it undergoes H(2)(+) transfer with substrates that react with oxygen anion by only proton transfer and therefore can be used to generate reactive ions not easily prepared by other methodologies.     

1-Decanethiol, a new reagent for the odorless deprotection of aryl methyl ethers

1-Decanethiol has been found to be an excellent reagent for the deprotection of aryl methyl ethers. This newly developed protocol afforded the corresponding phenols in good to excellent yields. A clear advantage of 1-decanethiol over the more commonly used thiols is the easy extraction of both the deprotecting reagent and the reaction byproduct into the aqueous phase, which allows an essentially odorless work-up.     

A new sensitive reagent for identifying Ag(+) and Hg(2+)

This paper describes the synthesis of a new reagent: N,N′-difuroyl thiourea for the purpose of improving coordination capacity of thiourea compounds. It has been characterized by IR, UV, MS and ¹H-NMR as well as elemental analytical data. According to the studies on its analytical performance, it is found that this reagent can be used to identify Ag⁺ and Hg²⁺. Both of their sensitivities and selectivities are the best in all methods for the time being. The new methods are simple and convenient, and can provide satisfactory results on synthetic and standard samples.     

A visual test paper for extremely strong concentrated acidity with a new synthesized isoindole reagent

A visual test paper by taking common filter paper as solid support for extremely strong concentrated acidity has been developed in this contribution with a new synthesized isoindole compound starting from p-phenylenediamine and the coupled fluorogenic reagent of o-phthaldialdehyde-β-mercaptoethanol. It was very easy for semiquantitative detection of acidity in the range of 0.2-18 M ([H⁺]) in extreme acidic solution based on the color changes of the solution or the visual test paper prepared by immerging filter paper slides into the solution of the new synthesized reagent. Quantitative detection of concentrated strong acids could be successfully constructed through the linear relationship exists between the absorbance of the chromogenic reagent at 510 nm and the acid concentrations.     

Synthesis of (+)-didesmethylmethylenomycin A methyl ester

A concise and efficient synthesis of the new compound—(+)-didesmethylmethylenomycin A methyl ester from chiral building block 4 has been achieved.     

Palladium-catalyzed asymmetric allylic alkylation with an enamine as the nucleophilic reagent

An enamine can serve as a good nucleophile for palladium-catalyzed asymmetric allylic alkylation, avoiding the use of an unstablilized ketone enolate formed by strong bases. In the presence of a palladium complex of chiral metallocene-based phosphino-oxazoline ligands, the reaction was carried out smoothly with high catalytic activity and excellent enantioselectivity. Different distances between the two Cp rings of ferrocene and ruthenocene affected the catalytic behavior in the reaction. Furthermore, high catalytic activity and good enantioselectivity were also afforded by the ferrocene-based diphosphine ligands with only planar chirality.     

2-(Diethylamino)ethanethiol, a new reagent for the odorless deprotection of aromatic methyl ethers

A new reagent for the deprotection of aromatic methyl ethers, 2-(diethylamino)ethanethiol, is reported. This compound, commercially available as its HCl salt, affords the corresponding phenols in good to excellent yields on a wide variety of substrates. A clear advantage of this method over the use of more common thiols, such as ethanethiol, is the easy extraction of both the deprotecting reagent and the byproduct 2-(diethylamino)ethyl methyl sulfide into the aqueous phase by quenching with dilute acid, which allows an essentially odorless workup.     

Structure and nucleophilic reactivity of aliphatic amines. A new opinion

Nucleophilic reactivity of alkylamines is determined by steric effect of the alkyl radicals. On the one hand, this effect hampers interaction of the reactant molecules and, on the other, changes bond angles at the nitrogen atom, thus favoring rehybridization of the unshared electron pair which is responsible for the ability of amines to act as nucleophiles.     

A new, enantioselective synthesis of (+)-isolaurepan

A highly enantioselective synthesis of 2,6-syn-disubstituted tetrahydropyrans from commercially available tri-O-acetyl-d-glucal, based on a thermal Claisen rearrangement, allows enantioselective synthesis of (+)-isolaurepan when combined with a ring expansion reaction using trimethylsilyldiazomethane.     

Fast Grey R.A. as a new colorimetric reagent

Summary Fast Grey R.A. dye can be used for the colorimetric microdetermination of vanadium in the limits of 0.01 to 1 ppm with a sensitive photometer and 0.05 to 8 ppm with a Beckman instrument, at 560 m. A large number of cations and anions up to 10 fold the vanadium amount do not interfere with its determination. Interference due to ferric iron up to an average of 40 fold or copper up to 2 fold the vanadium concentration is simply eliminated by reduction with ascorbic acid and heating in the case of iron or by the same treatment and the addition of ammonium thiocyanate solution in the case of copper.Part II: See Z. analyt. Chem. 158, 103 (1957).     

The absolute configurations of (+)-thalictrifoline and (+)-corydalic acid methyl ester. Total synthesis of (+)-thalictrifoline.

(+)-Thalictrifoline ($\text{3}$) has been synthesized from an optically resolved (+)-8-oxo-13-carboxytetrahydroprotoberberine ($\text{13}$) whose absolute configuration was established by correlation with (+)-$\text{18}$. This determines the absolute configurations of (+)-thalictrifoline ($\text{3}$) as 13R, 14R aria (+)-corydalic acid methyl ester ($\text{9}$) as 3R, 4R.     

A new colorimetric reagent for molybdenum

Disodium-1,2-dihydroxybenzene-3,5-disulfonate (“Tiron”) gives a bright yellow color with molybdenum(VI). Under optimum conditions (wavelength 390 mμ and pH 6.6-7.5) the sensitivity of this reaction is about 1 part of molybdenum in 10,000,000 parts of solution, when measurements are made on a Beckman Model DU Spectrophotometer using a 1-cm cell.An extensive study on the use of Tiron for the determination of molybdenum in a variety of materials is under way.     

A new reagent for direct difluoromethylation

Molecular scaffolds containing alkylfluorine substituents are desired in many areas of chemical research from materials to pharmaceuticals. Herein, we report the invention of a new reagent (Zn(SO(2)CF(2)H)(2), DFMS) for the innate difluoromethylation of organic substrates via a radical process. This mild, operationally simple, chemoselective, and scalable difluoromethylation method is compatible with a range of nitrogen-containing heteroarene substrates of varying complexity as well as select classes of conjugated π-systems and thiols. Regiochemical comparisons suggest that the CF(2)H radical generated from the new reagent possesses nucleophilic character.