Presence Of Chlorotrimethylsilane Research Articles

Facile synthesis of silyl allenol ethers and β-silyl enones through reductive silylation of benzoylacetylenes

Reductive silylation of benzoylacetylenes by magnesium metal in the presence of chlorotrimethylsilane in N,N-dimethylformamide (DMF) gave silyl allenol ethers or β-silyl enones. Isolation of silyl allenol ethers was found to require a careful treatment and only hydrolyzed β-silyl enones were formed in some cases. Diverse multisubstituted allenol silyl ethers and β-silyl enones with good functional group tolerance were selectively synthesized in 38–86% and 23–88% yields under mild reaction conditions.

Synthesis of new α-hydroxyphosphonates and α-acetoxyphosphonates

ABSTRACTA series of new α-hydroxyphosphonate (5–14) have been synthesized in high yields by reaction of β-chloro-α,β-unsaturated aldehydes (1–4) and trialkyl phosphite in the presence of chlorotrimethylsilane at room temperature under solvent-free conditions. In addition, compounds (5–14) were reacted with acetic anhydride in DBU to give the new α-acetoxyphosphonate derivatives (15–23). All these phosphonates (5–23) were obtained as mixtures of two (E and Z) isomers and fully characterized by multinuclear (1H, 13C, and 31P) NMR, IR spectroscopy and HRMS.

Rhodium(I)-Complexes Catalyzed 1,4-Conjugate Addition of Arylzinc Chlorides to N-Boc-4-pyridone.

Rhodium(I)-complexes catalyzed the 1,4-conjugate addition of arylzinc chlorides to N-Boc-4-pyridone in the presence of chlorotrimethylsilane (TMSCl). A combination of [RhCl(C2H4)2]2 and BINAP was determined to be the most effective catalyst to promote the 1,4-conjugate addition reactions of arylzinc chlorides to N-Boc-4-pyridone. A broad scope of arylzinc reagents with both electron-withdrawing and electron-donating substituents on the aromatic ring successfully underwent 1,4-conjugate addition to N-Boc-4-pyridone to afford versatile 1,4-adducts 2-substituted-2,3-dihydropyridones in good to excellent yields (up to 91%) and excellent ee (up to 96%) when (S)-BINAP was used as chiral ligand.

Reductive carboxylation of aromatic esters by electron transfer from magnesium metal

Magnesium-promoted reductive carboxylation of ethyl benzoate in the presence of chlorotrimethylsilane in N,N-dimethylformamide brought about a new carbon-carbon bond formation between the carbonyl carbon atom and carbon dioxide to give the corresponding benzoylformic acid in good yield. It is noteworthy that only ethyl benzoates with substituents at the meta-position were converted into benzoylformic acid derivatives. Moreover, no mandelic acid was detected even under the reductive conditions. This result indicates that benzoylformic acid was obtained after hydrolysis of a carboxylated intermediate, which would be alive as a stabilized structure in the reaction media.

ChemInform Abstract: Selective Introduction of a Trifluoroacetyl Group onto 4‐Vinylpyridines Through Magnesium‐Promoted Reduction.

Abstract Magnesium-promoted reductive coupling of 4-vinylpyridines and ethyl trifluoroacetate in the presence of chlorotrimethylsilane in N-methyl-2-pyrrolidone resulted in selective formation of the trifluoroacetylated compounds at the β-olefinic carbon of the pyridine ring, the electron deficient carbon in good yields. In particular, 4-vinylpyridine with an aromatic ring at the β-olefinic position of the pyridine ring gave higher yield of the trifluoroacetylated compound. The nitrogen atom of the pyridine ring may play an important role in the regioselectivity of the product.

Selective introduction of a trifluoroacetyl group onto 4-vinylpyridines through magnesium-promoted reduction

Magnesium-promoted reductive coupling of 4-vinylpyridines and ethyl trifluoroacetate in the presence of chlorotrimethylsilane in N-methyl-2-pyrrolidone resulted in selective formation of the trifluoroacetylated compounds at the β-olefinic carbon of the pyridine ring, the electron deficient carbon in good yields. In particular, 4-vinylpyridine with an aromatic ring at the β-olefinic position of the pyridine ring gave higher yield of the trifluoroacetylated compound. The nitrogen atom of the pyridine ring may play an important role in the regioselectivity of the product.

(E)-Trimethyl(perfluoroprop-1-enyl)silane As a Reagent to Transfer Perfluoroprop-1-enyl Group to Ketones and Aldehydes Catalyzed by Fluoride

Analogous to trifluoromethyltrimethylsilane (Ruppert’s reagent) (E)-trimethyl(perfluoroprop-1-enyl)silane (1), prepared by deprotonation of (Z)-1,2,3,3,3-pentafluoroprop-1-ene (2a) at −78 °C in the presence of chlorotrimethylsilane, was shown to transfer the perfluoroprop-1-enyl group to a number of electrophiles containing carbonyl group in the presence of catalytic amount of fluoride anion. The perfluoroprop-1-enyl group was transferred to formaldehyde, acetaldehyde, benzaldehyde, acetone, trifluoroacetophenone resulting in formation of corresponding TMS-ethers of secondary and tertiary alcohols containing Z-CF3CF═CF– fragment. With some substrates such as hexafluoroacetone, formaldehyde, and trifluoroacetophenone, substituted 5-membered dioxolane products of the reaction can be obtained, depending on the reaction conditions and the source of fluoride catalyst.

Chelation-Controlled Additions to α-Silyloxy Aldehydes: An Autocatalytic Approach

The Felkin-Anh model has been widely accepted to describe stereochemical outcomes in nucleophilic additions to α-silyloxy carbonyl compounds. Herein, it is demonstrated that chelation-controlled additions can be performed using dialkylzinc reagents in the presence of chlorotrimethylsilane with good to excellent diastereoselectivities. Ethyl zinc chloride, the Lewis acid responsible for promoting chelation, is generated in situ in an autocatalytic fashion. This approach circumvents its use in stoichiometric amounts.

Efficient Synthesis of 2,3‐Disubstituted‐1,3‐benzoxazines by Chlorotrimethylsilane‐Mediated Aza‐Acetalizations of Aromatic Aldehydes

A series of novel substituted 3,4‐dihydro‐2H‐1,3‐benzoxazines were prepared in moderate to good yields by aza‐acetalizations of aromatic aldehydes with 2‐(N‐substituted aminomethyl)phenols in the presence of chlorotrimethylsilane or SnCl4. It was found that chlorotrimethylsilane was more effective for the reaction, especially for the reaction of fluorobenzaldehyde, and thereby, an efficient method for the preparation of 3,4‐dihydro‐2H‐1,3‐benzoxazines was developed. The structures of the compounds were determined by FT‐IR, 1H NMR, 13C NMR, MS, and elemental analysis.

Conjugate Addition Reactions of N-Carbamoyl-4-pyridones and 2,3-Dihydropyridones with Grignard Reagents in the Absence of Cu(I) Salts

N-Boc- and N-ethoxycarbonyl-4-pyridones and the resulting 2,3-dihydropyridones undergo 1,4-addition reactions with Grignard reagents in the presence of chlorotrimethylsilane (TMSCl) or BF3·Et2O in excellent yields. Copper catalysis is not required, and mechanistic considerations suggest that the reaction is proceeding by a conjugate addition pathway rather than by a pathway involving 1,2-addition to an intermediate pyridinium ion. TMSCl-mediated conjugate addition of Grignard reagents to 2-substituted-2,3-dihydropyridones gives the trans-2,6-disubstitued piperidinones stereoselectively, while cuprate reagents give either the trans or cis diastereomers or mixtures.

Electroreductive intramolecular coupling of aliphatic cyclic imides with α,β-unsaturated esters and ketones: unusual methyl-alkoxy exchange in silyl ketene acetals

Abstract The electroreductive intramolecular coupling of aliphatic cyclic imides with α,β-unsaturated esters in the presence of chlorotrimethylsilane and subsequent desilylation with TBAF gave five- and six-membered cyclized esters and one-carbon elongated methyl ketones. These methyl ketones were formed by methyl-alkoxy exchange in intermediate silyl ketene acetals. The same methyl ketones were also obtained by the electroreductive intramolecular coupling of aliphatic cyclic imides with α,β-unsaturated methyl ketones. The cyclized methyl ketones were transformed to the known indolizidine and quinolizidine alkaloids, (±)-tashiromine and (±)-epilupinine.

Synthesis, Molecular Structure, and Catalytic Evaluation of Centrostereogenic Ferrocenophane Phosphines

1,1′-[(1R)-1-Diarylphosphino-1,3-propanediyl]ferrocenes, where aryl = phenyl, 2-tolyl, 4-tolyl, mesityl, 4-anisyl, 4-(trifluoromethyl)phenyl, were prepared as new chiral ferrocenophane phosphines featuring only central chirality in good yields by the reaction of the corresponding chiral alcohol, 1,1′-[(1R)-1-hydroxy-1,3-propanediyl]ferrocene, and diarylphosphines in the presence of chlorotrimethylsilane and sodium iodide. These phosphines were studied as ligands in palladium(II) complexes and further evaluated in two mechanistically different model catalytic reactions, namely in Pd-catalyzed asymmetric allylic alkylation of 1,3-diphenylallyl acetate with dimethyl malonate, and in enantioselective aza-Morita-Baylis-Hillman reactions of aromatic N-sulfonyl imines with methyl vinyl ketone.

Efficient Synthesis of Arylaldehyde Oxime Ethers Functionalised with 3,4-dihydropyrimidinones and 2,5-quinazolinediones via a One-pot Two-step Method

New arylahdehyde oxime ethers functionalised with N3-3,4-dihydropyrimidinone and 2,5-quinazolinedione groups were synthesised in moderate to good yields by the reaction of the corresponding 3,4-dihydropyrimidinones and quinazolinediones with paraformaldehyde and arylaldehyde oximes via a one-pot two-step strategy in the presence of chlorotrimethylsilane. The advantages of this method are the simple procedure, the high regioselectivity of the products and the mild reaction conditions.

Regioselective coupling reaction of azulene with α,β-unsaturated ketones by Mg-promoted reduction

Mg-Promoted reductive coupling of azulene with various α,β-unsaturated ketones in the presence of chlorotrimethylsilane in 1-methyl-2-pyrrolidinone brought about regioselective formation of the corresponding 6-substituted dihydroazulenes, which were easily oxidized to the corresponding 6-substituted azulenes by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone in good yields. This new regioselective method enabled us to synthesize various 6-substituted azulenes from azulene in only two steps.

Electroreductive intermolecular coupling of phthalimides with aldehydes: application to the synthesis of alkylideneisoindolin-1-ones

The electroreduction of N-methyl, N-p-anisyl, and N-unsubstituted phthalimides with aldehydes in the presence of chlorotrimethylsilane and triethylamine gave intermolecularly coupled products, 3-hydroxy-3-(1-hydroxyalkyl)isoindolin-1-ones. The coupling products were reduced with Et3SiH/BF3·Et2O to 3-(1-hydroxyalkyl)isoindolin-1-ones, which were dehydrated to alkylideneisoindolin-1-ones. From N-unsubstituted phthalimides, Z-isomers of alkylideneisoindolin-1-ones were obtained stereospecifically.

Nucleophilic Pentafluorophenylation of Nitroalkenes

The interaction of pentafluorophenylmagnesium bromide with conjugate nitroalkenes is described. The optimized conditions involve performing the reaction either in diethyl ether in the presence of chlorotrimethylsilane or in a tetrahydrofuran–diethyl ether solvent mixture. The addition products can be transformed into 4,5,6,7-tetrafluoroindolines by means of a reduction and cyclization sequence.

Electroreduction of Triphenylphosphine Oxide to Triphenylphosphine in the Presence of Chlorotrimethylsilane

Electroreduction of triphenylphosphine oxide to triphenylphosphine in an acetonitrile solution of tetrabutylammonium bromide in the presence of chlorotrimethylsilane was performed successfully in an undivided cell fitted with a zinc anode and a platinum cathode under constant current. A plausible mechanism involving, (1) one-electron reduction of triphenylphosphine oxide generating the corresponding anion radical [Ph 3 P˙-O - ], (2) subsequent reaction with chlorotrimethylsilane affording the (trimethylsiloxy)triphenylphosphorus radical [Ph 3 P˙-OSiMe 3 ], and (3) further one-electron reduction followed by P-O bond fission leading to triphenylphosphine is proposed. In a similar manner, electroreduction of some triarylphosphine oxides and alkyldiarylphosphine oxides was executed to give the corresponding phosphine derivatives in good to moderate yields.

Electroreductive Intramolecular Coupling of Phthalimides with Aromatic Aldehydes: Application to the Synthesis of Lennoxamine

The electroreductive intramolecular coupling of phthalimides with aromatic aldehydes in the presence of chlorotrimethylsilane and triethylamine led to five-, six-, and seven-membered cyclized products (58-84%). The electroreductive cyclization was applied to the total synthesis of lennoxamine.

Diastereoselective intermolecular coupling of chiral α-imino amides with ketones by electroreduction

The electroreductive intermolecular coupling of chiral α-imino N, N-dialkylamides derived from ( S)-α-amino N, N-dialkylamides and aromatic aldehydes with ketones in the presence of chlorotrimethylsilane and triethylamine gave β-amino alcohols with moderate to good ( R)-stereoselectivity.

1,3-Bis(pyren-1-yl)imidazolium chloride (IPyr·HCl)

A novel UV-A-light absorbing N-heterocyclic carbene precursor imidazolium salt 2 was synthesized by reaction of 1,4-bis(pyren-1-yl)-1,4-diazadiene 1 with paraformaldehyde in the presence of chlorotrimethylsilane. The title compound was characterized by 1H-NMR, 13C-NMR, 2D-NMR, mass spectrometry, IR and UV/VIS spectroscopy.