Alexander I. Albanov

The reaction of N-trimethylsilyl-amides and -lactams with dimethyl(chloromethyl)chlorosilane. Kinetically controlled formation of (NSi) chelate intermediates, O-[(dimethylchlorosilyl)methyl]imidates and their rearrangement to final(OSi) chelate N-[(dimethylchlorosilyl)methyl]amides and lactams

The multistage character of the reaction of dimethyl(chloromethyl)chlorosilane (I) with N-trimethylsilyl-amides and -lactams (II) was shown by NMR monitoring. Interaction of the reactants starts with transsilylation, leading to Me3SiCl and the corresponding N-[dimethyl(chloromethyl)silyl]amide or -lactam (III). The second stage, intramolecular (dimethylchlorosilyl)methylation of unstable III, proceeds in two directions. A kinetically controlled transformation of III affords previously unknown O-(dimethylchlorosilyl)methylated intermediates, O-[(dimethylchlorosilyl) methyl]imidates (IV) containing a hypervalent ClSiN bond. The already known products, (OSi) chelate N-[(dimethylchlorosilyl)methyl]amides (V), arise from the reaction carried out under thermodynamic control. The same compounds are also formed via the Chapman rearrangement of the intermediates (IV).

Synthesis and Ag+-catalyzed cyclization of 2,3-dienamides

Abstract Reaction of 1-lithiated methoxyallene and lithiated 3-methyl-1,2-butadiene with isocyanates, RNCO (R=alkyl) followed by hydrolysis affords the dienamides H 2 CCC(OCH 3 )C(O)NHR and (CH 3 ) 2 CCCHC(O)NHR, respectively, in good to excellent yields. Cyclization to 2-(5 H )-furanylidenamines or mixtures of these compounds with 1,5-dihydro-2 H- pyrrol-2-ones can be achieved with silver acetate or silver nitrate in acetone.

trans-Silylation of silatranes and 1,2-dimethyl-2-azasilatran-3-one by Si-substituted trimethoxysilanes

Abstract trans- Silylation of silatranes by Si-substituted trimethoxysilanes has been found to be a reversible reaction, the equilibrium of which is shifted towards the formation of the silatrane bearing a stronger (shorter) transannular N→Si bond. A related reaction of 1,2-dimethyl-2-azasilatran-3-one with Si-substituted trimethoxysilanes leads to products in good yields only when phenyltrimethoxysilane is used.

Electrophilic Cyclization of Dimethyl(ω-phenylaminoalkyl)alkenylsilanes

Unsaturated organosilicon amines [CH2 = CH(CH2)n]Me2Si[(CH2)mNHPh] at the action of Hg(OAc)2 in THF solution transform to corresponding heterocycles. Regioselectivity of this intramolecular electrophilic heterocyclization is defined by the position of double bond relatively to the silicon atom. This is caused by β-effect of the silyl group.

CHEMO- AND STEREOSELECTIVE ADDITION OF DIORGANYLPHOSPHINE OXIDES TO α,β-ETHYLENIC ALDEHYDES

Secondary phosphine oxides (R1)2P(O)H 1–3 react with α,β-ethylenic aldehydes R2CH=CHC(O)H 4–6 under mild conditions (THF, 22–42°C) to form chemo- and stereoselectively hydroxyethenylphosphine oxides (R1)2P(O)CH(OH)CH=CHR2 (E) 7a–h in high yield.

Experimental and theoretical study of the intramolecular C–H···N and C–H···S hydrogen bonding effects in the 1H and 13C NMR spectra of the 2-(alkylsulfanyl)-5-amino-1-vinylpyrroles: a particular state of amine nitrogen

In the 1H NMR spectra of the 1‐vinylpyrroles with amino‐ and alkylsulfanyl groups in 5 and 2 positions, an extraordinarily large difference between resonance positions of the HA and HB terminal methylene protons of the vinyl group is discovered. Also, the one‐bond 1J(Cβ,HB) coupling constant is surprisingly greater than the 1J(Cβ,HA) coupling constant in pyrroles under investigation, while in all known cases, there was a reverse relationship between these coupling constants. These spectral anomalies are substantiated by quantum chemical calculations. The calculations show that the amine nitrogen lone pair is removed from the conjugation with the π‐system of the pyrrole ring so that it is directed toward the HB hydrogen. These factors are favorable to the emergence of the intramolecular C–HB•••N hydrogen bonding in the s‐cis(N) conformation. On the other hand, the spatial proximity of the sulfur to the HB hydrogen provides an opportunity of the intramolecular C–HB•••S hydrogen bonding in the s‐cis(S) conformation. Presence of the hydrogen bond critical points as well as ring critical point for corresponding chelate ring revealed by a quantum theory of atoms in molecules (QTAIM) approach confirms the existence of the weak intramolecular C–H•••N and C–H•••S hydrogen bonding. Therefore, an unusual high‐frequency shift of the HB signal and the increase in the 1J(Cβ,HB) coupling constant can be explained by the effects of hydrogen bonding. Copyright

Reaction of Red Phosphorus with Allylbenzene in Superbasic System KOH-DMSO

Abstract Red phosphorus reacts with allylbenzene in the superbase system KOH-DMSO (130°C, 3 h, Ar) to give a mixture of bis(1-methyl-2-phenylethyl)phosphane (1), bis(1-methyl-2-phenylethyl)phosphane oxide (2), and 1-methyl-2-phenylethylphosphinic acid (3). Secondary phosphane oxide 2 and phosphinic acid 3 have been isolated from this mixture in 35% and 32% yield, respectively. Microwave activation of the reaction (200 W, 30 min) affords secondary phosphane 1 as the main product in 48% yield. GRAPHICAL ABSTRACT

Dithiobiuretes in reactions with electrophilic acetylenes. New derivatives of 1,3,5-dithiazines,-thiadiazines and-triazines as the products of competing reactions of nucleophilic cycloaddition

The nucleophilic addition of 2,4-dithiobiurete, 1- and 1,4-substituted 2,4-dithiobiuretes (2 a-e) with benzoylacetylene (1) has been studied. 2-(Benzoylmethyl)-4-(R1-imino)-6-(R2-imino)dihydro-4H-1,3,5-dithiazinium perchlorates (3 a-e) are obtained in glacial acetic acid (AcOH) in the presence of equimolar quantities of HClO4. The reaction of benzoylacetylene with 1,5-diphenyl-2,4-dithiobiurete in either of MeOH, C6H6, or MeCN solvents proceeds non-selectively to give a mixture of products such as 2-(benzoylmethyl)-4,6-di(phenylimino)dihydro-4H-1,3,5-dithiazine (5), 2-(benzoylmethyl)-4-(β-benzoylvinyl)thio-3-phenyl-6-(phenylimino)-3,6-dihydro-2H-1,3,5-thiadiazine (8), 2-(benzoylmethyl)-1,3-diphenylhexahydro-1,3,5-triazine-4,6-dithione (7) and N-(β-benzoylvinyl)-N-phenylthioureas (6).

Synthesis, molecular structure, conformational analysis, and chemical properties of silicon-containing derivatives of quinolizidine.

A silicon analog of quinolizidine 3,3,7,7-tetramethylhexahydro-1H-[1,4,2]oxazasilino[4,5-d][1,4,2]oxazasilin-9a-yl)methanol 3 was synthesized. X-ray diffraction analysis confirmed the trans configuration and low temperature NMR spectroscopy both the flexibility (barrier of interconversion 5.8 kcal mol(-1)) and the conformational equilibrium (chair-chair and chair-twist conformers) of the compound. The relative stability of the different isomers/conformers of 3 was calculated also at the MP2/6-311G(d,p) level of theory. Intra- and intermolecular hydrogen bonding in 3 and the appropriate equilibrium between free and self-associated molecules was studied in solvents of different polarity. Both the N-methyl quaternary ammonium salt and the O-trimethylsilyl derivative of 3 could be obtained and their structure determined.

Study of stereospecificity of 1H, 13C, 15N and 77Se shielding constants in the configurational isomers of the selenophene-2-carbaldehyde azine by NMR spectroscopy and MP2-GIAO calculations

In the 1H and 13C NMR spectra of selenophene‐2‐carbaldehyde azine, the 1H‐5, 13C‐3 and 13C‐5 signals of the selenophene ring are shifted to higher frequencies, whereas those of the 1H‐1, 13C‐1, 13C‐2 and 13C‐4 are shifted to lower frequencies on going from the EE to ZZ isomer or from the E moiety to the Z moiety of EZ isomer. The 15N chemical shift is significantly larger in the EE isomer relative to the ZZ isomer and in the E moiety relative to the Z moiety of EZ isomer. A very pronounced difference (60–65 mg/g) between the 77Se resonance positions is revealed in the studied azine isomers, the 77Se peak being shifted to higher frequencies in the ZZ isomer and in the Z moiety of EZ isomer. The trends in the changes of the measured chemical shifts are reasonably reproduced by the GIAO calculations at the MP2 level of the 1H, 13 C, 15 N and 77Se shielding constants in the energy‐favorable conformation with the syn orientation of both selenophene rings relative to the C = N groups. The NBO analysis suggests that such an arrangement of the selenophene rings may take place because of a higher energy of some intramolecular interactions. Copyright