Synthesis and characterization of 4-dimethylamino-N-triphenylmethylpyridinium chloride,a postulated intermediate in the tritylation of alcohols

4-Dimethylamino-$\text{N}$-triphenylmethylpyridinium chloride ($\text{1}$) reacts with primary but not secondary alcohols to produce trityl ethers in good yield; in addition, amines may be selectively $\text{N}$- tritylated witth $\text{1}$ in the presence of alcohols.     

Reductive cleavage of axially disymmetric tertiary amines and quaternary ammonium salts by lithium aluminium hydride. Synthesis of new 1,1′-binaphthyl substituted amines

Axially disymmetric tertiary amines or quaternary ammonium salts $\text{A}$ are synthesized by double alkylation of primary or secondary amines with racemic or optically pure 2,2′-bis (bromomethyl)-1,1′-binaphthyl. Their reductive cleavage by lithium aluminium hydride in refluxing THF leads to chiral secondary or tertiary amines $\text{B}$, substituted by a binaphthyl unit, with high yields and absence of racemization.     

Transition structures for the reaction of difluorocarbene with propene

Two $\text{ab}$$\text{initio}$ transition structures for the reaction of difluorocarbene with propene have been located with gradient techniques and the 3-21G basis set. The activation energy is 1.3 kcal/mol lower than for the reaction with ethylene. Two transition structures with the fluorines approaching $\text{syn}$ or $\text{anti}$ to the methyl group are identical in energy     

Synthesis of sterically hindered 1-arylpyrrolidines and 1-arylpiperidines by condensation of primary aromatic amines with cyclic ethers or diols

A variety of 1-($\text{o}$-alkylphenyl)- and 1-($\text{o}$-$\text{o}$'-dialkylphenyl)- pyrrolidines and -piperidines were prepared by the gas phase alumina mediated condensation of tetrahydrofuran (THF), tetrahydropyran (THP) or the corresponding diols with primary aromatic amines in fair to high yield. This methodology can also be used for the synthesis of 1-phenylhexahydroazepine from aniline. A mechanistic interpretation of the catalytic action of alumina is presented.     

Some advances in the liquid-phase autoxidation of organic compounds of the non-transitional elements

Dicrotylzinc (I) adds to CC double bonds in olefins even at temperatures between 20 and 60°. With ethylene bis(3-methyl-4-pentenyl)zinc (II) is formed selectively, and with 1-octene the $\text{1}\text{1}$ adduct as which is derived from the 1-methyl-2-propenyl form of (I) is formed almost exclusively. In the reactions with styrene and butadiene metal-to-C(1) addition competes with metal-to-C(2) addition: with butadiene, products which are derived from the 2-butenyl structure of (I) are formed in only 3–13% yield. In comparison with crotylmagnesium and crotylaluminium, (I) reacts more selectively to give products derived from the 1-methyl-2-propenyl form.     

Some syntheses using tetrakis(trifluoromethyl)dewar thiophene

Tetrakis(trifluoromethyl)Dewar thiophene ($\text{1}$) is found to be a good dipolarophile and dienophile. Therefore, $\text{1}$ reacts with any kind of azides to give 1,3-dipolar cycloadducts, which are transformed to tetrakis(trifluoromethyl)Dewar pyrroles ($\text{2}$), compounds of a new cyclic ring system. Further, $\text{1}$ reacts with cyclic or acyclic dienes to give Diels-Alder adducts. The adduct ($\text{3}$) of $\text{1}$ with butadiene was transformed to tetrakis(trifluoromethyl)cyclooctatetraene ($\text{4}$) by desulfurization, bromination and dehydrobromination, stepwise. Valence-bond isomerisation of $\text{4}$ will be presented.

     

A new stereoselective synthesis of 2-subsdtituted 1,3-bis(trimethylsilyl)propene derivatives and their conversion to cyclopentane and cyclohexane derivatives

Ester $\text{2}$ on treatment with sodium salt of sulfone or sulfoxide afforded 2-substituted 1,3-bis(trimethylsily)propene $\text{3}$ in good yield, from which cyclopentane and cyclohexane derivatives bearing a trimethylsilyl group in the molecules were synthesized.     

Experimental tests of the stereoelectkoic effect at phosphoru: Michaelis-Arbusov reactivity of phosphite esters

Whereas triethyl phosphite readily reacts with benzoyl chloride to yield the Michaelis-Arbusov product, diethyl benzoyl phosphonate, 1-methyl-4-phospha-3,5,8-trioxabi)cyclo[2.2.2]octane, $\text{1}$, is essentially unreactive, even at a higher temperature. The bicyclic phosphite $\text{1}$ also reacts slower than the triethyl phosphite $\text{2}$ In an oxidation with t-butyl hydroperoxide. These results are interpreted in terms of the stereoelectronic effect.     

The photolysis of platinacycloalkanes in solution

The photolysis of [I₂$\text{PtCH}{}_2\text{CH}{}_2\text{CH}{}_2\text{C}$H₂ (PMe₂ Ph)₂] gives ethylene and but-1-ene as volatile products, the latter probably being formed via a five-coordinate platinum intermediate. However, the formation of propene from the photolysis of [Cl₂$\text{PtCH}{}_2\text{CH}{}_2\text{C}$H₂ (1,10-phenanthroline) appears to involve a direct transfer of a hydrogen atom between neighbouring CH₂ groups in the ring. Other gaseous products, e.g. cyclopropane, ethylene, may be formed via a platinum ion radical.     

A facile one-pot preparation of 2-methyl-and 2-phenyl-4- fluoro-5-trifluoromethyl-6-methoxypyrimidine from methyl 2-hydryl-2-(F-methyl)-F-propyl ether

The title compounds were readily prepared in one-pot by phase-transfer reaction of a methanol adduct of 2-($\text{F}$-methyl)-$\text{F}$- propene with acetamidine or benzamidine in the presence of aqueous sodium hydroxide in CH₂Cl₂. Various 5-trifluoromethyl- pyrimidines were also synthesized $\text{via}$ nucleophilic substitution of the 4-fluorine of the title compounds.     

Synthesis of silylated methylenecyclopropanes

2-Trimethylsilylmethylenecyclopropane (=3) was synthesized by reaction of lithio methylenecyclopropane with TMSCl. The lithium salt of (=3) reacts with some electrophiles by α- or γ-attack depending on the nature of the electrophile. Whereas alkenylbromides $\text{8}$ and $\text{9}$ or alkinylbromide $\text{10}$ give exclusively α-attack, benzaldehyde reacts with γ-alkylation.     

O- versus N-methanesulphonylation and N-(methanesulphonyl)-methanesulphonylation with methanesulphonyl chloride

Depending upon the experimental conditions, t-butyl (1$\text{SR}$,5$\text{SR}$,7$\text{RS}$,8$\text{RS}$)-1-ethoxycarbonyl-8-hydroxy-2-oxa-6-azabicyclo[3.2.0]octane-7-carboxylate (2a) reacts with methanesulphonyl chloride to give predominantly the $\text{O}$-methanesulphonyl derivative (2b), the $\text{N}$-methanesulphonyl derivative (3a), or the $\text{N}$-(methanesulphonyl)methane-sulphonyl derivative (6a).     

A stereocontrolled synthesis of Z and E terminal dienes from pinacol E-1-trimethylsilyl-1-propene-3-boronate

Pinacol $\text{E}$-1-trimethylsilyl-1-propene-3-boronate reacts with aldehydes to form (±)-($\text{R}$*,$\text{S}$*)-3-trimethylsilyl-4-hydroxy-1-alkenes, which can be deoxysilylated stereoselectively to either 98% $\text{Z}$ or 99% $\text{E}$ 1,3-dienes, including the separate components of the red bollworm moth pheromone.     

Stereoselektive c-glycosidsynthese durch titan-(iv)-katalysierte addition von silylenolethern an 2-acyloxy-3-keto-glycale

C-Glycosides are stereoselectively formed by the titan-(IV)-catalysed addition of silyl enolethers $\text{2}$ to 2,4,6-tri-O-acyl-1-deoxy-D-erythro-hex-1-enopyran-3-uloses $\text{1}$ followed by elimination of the 4-acyloxy substituent. Cyclohexenyl silylether $\text{2a}$ reacts with 2-acetoxy-3-keto-glycal derivative $\text{la}$ forming only one product $\text{3a}$. Thus, the reaction seems to be diastereospecific with respect to both new chiral centers of the product.     

A highly efficient and general N-monomethylation of functionalized primary amines via formylation--borane:methyl sulfide reduction

Formylation of functionalized primary aromatic and aliphatic amines with acetic formic anhydride (AFA) followed by borane:methyl sulfide reduction in the same pot affords the corresponding $\text{N}$-methylamines in excellent isolated yields, uncontaminated bybis alkylation; the reaction sequence is applicable to even very weakly basic and sterically hindered amines.     

Stereospecific formation of amidines by 1,1-addition of amines to isocyanides

Addition of secondary amines to isonitriles in the presence of AgCl at low temperature gives isolable but thermodynamically unstable Z-amidines; only the more stable $\text{6E}$ undergoes ring expansion to the imidazoline $\text{7}$.     

Primary amines via electrophilic amination of organometallic compounds with o-(diphenylphosphinyl)hydroxylamine

It is shown that O-(diphenylphosphinyl)hydroxylamine $\text{4a}$ transforms all kinds of “carbanions” into primary amines; best yields are received with “stabilized anions”, e.g. of the benzylic type.     

Rearrangement of 10-oxabenzo-syn-sesquinorbornene by light and by acids

10-Oxabenzo-$\text{syn}$-sesquinorbornene ($\text{1}$) is rearranged by either UV irradiation or strong acid to 2,3-norborneno-1-naphthol ($\text{5}$), whose methyl ether is formed by the acid rearrangement in the presence of methanol. The mechanism of the acid rearrangement is discussed. With strong acid, cyclopentadiene reacts with 1-naphthol to yield 2- and 4-cyclopentenyl-1-naphthols.     

Nucleophilic reactions of fluoroolefins. I. Reactions of 1-(2-tetrahydrofuryl)-pentafluoropropene with alkoxide ions

Unlike unsubstituted perfluoropropene [1,2] 1-(2-tetrahydrofuryl)-pentafluoropropene $\text{1}$ reacts with sodium alkoxides in parent alcohol solutions to give 1-alkoxy-1-(2-tetrahydrofuryl)-tetrafluoropropenes $\text{2}$ as major products and 1-alkoxy-2H-1-(2-tetrahydrofuryl)-pentafluoropropanes $\text{3}$ as very minor products. The yield of adducts $\text{3}$ is, to some extent, increased by the reduced basicity of the alkoxide ion. Results are discussed in terms of the supposed properties of the carbanionic intermediates involved.N.m.r., m.s., and i.r. data for, and some chemical properties of compounds $\text{2}$, viz., further reactions with sodium alkoxides and hydrolysis are described.     

Fluorinated isocyanates - reactions with fluorinated anhydrides,acids, and related substrates

$\text{F}$-Phenylisocyanate reacts with cyclic or linear anhydrides with the aid of catalysts to form $\text{F}$-(N-arylimides) in good yields. Similar reactions with fluorinated acids lead directly to amides. This isocyanate undergoes smooth reaction with various substrates (hexafluoroacetone, trioctylphospine oxide, and itself). Several reactions between $\text{F}$-aryl and $\text{F}$-alkyl isocyanates are compared. Reaction between the latter and $\text{F}$-anhydrides or acids gives products derived from fluoride ion transfer reactions.