Acetylenic amides. 2. The generation and reactions of dianions derived from 2-propynamides

The dianion of N-benzyl-2-propynamide can be generated by the treatment of 4 with two equivalents of LDA at ?65° or ethylmagnesium bromide at ?20°. The trilithio species 6 is readily formed using 3 equivalents of LDA. Reaction of 5 with aldehydes or ketones produce hydroxypropynamides 9 in good yields. Silation of 5a with chlorotrimethylsilane produces N-benzyl-3-trimethylsilyl-2-propynamide ( 13 ) in high yield. Reduction of 9 furnishes either fully saturated amides 15 or partially reduced cis-olefins 16 or 18 . Compounds 16 , on heating, rearrange to 4-ketoamides 17 . Carboxylation of 5a with carbon dioxide produces 3-benzyl-2,4-dioxo-5-oxazidinylacetic acid ( 11 ). Warming 11 in dimethyl sulfoxide results in the loss of carbon dioxide and the formation of N-benzylpyruvamide ( 21 ).     

Reaction and characterization of thioamide dianions derived from N-benzyl thioamides

Thioamide dianions were generated by the highly efficient reaction of N-benzyl thioamides with 2 equiv of BuLi. Alkylation, allylation, and silylation took place selectively at the carbon atom adjacent to the nitrogen atom of the thioamide dianions. Oxiranes and an aldehyde were also used as electrophiles in the reaction of thioamide dianions to form N-thioacyl 1,3- or 1,2-amino alcohols. The insertion reaction of elemental sulfur to a thioamide dianion and subsequent ethylation afforded a N-thioacyl hemithioaminal. NMR studies on the thioamide mono- and dianions derived from N-benzyl 2-methoxythiobenzamide showed a linear relationship between the chemical shifts of all carbon atoms of thioamide mono- and dianions. The results also suggested that the negative charge at the benzylic carbon atom of the dianion is not fully delocalized. The charge distribution patterns of the dianion are consistent with those of pi polarization.     

Synthesis and frustrated phases of chiral liquid crystals derived from (R)-3-alkoxy-2-methylpropionic acids

A homologous series of chiral compounds, (R)-6-(3-alkoxy-2-methylpropionyloxy)-2-naphthyl 4-alkoxybenzoates, nMPNmB (n = 2-5, m = 6-13), derived from methyl (R)-3-hydroxy-2-methylpropionate, was prepared for the study of mesormorphic phases. The mesophases were determined mainly by their microscopic textures and identified by the racemic modification. The results show that most of these compounds displayed frustrated phases BP, TGB_A* and TGB_C*, and the N*phase. Moreover, the thermal stability of the frustrated phases is significantly affected by the length of the alkyl chain in both achiral and chiral groups of the compounds. The spontaneous polarization in the TGB_C* phase of compounds nMPN10B in a surface-stabilized geometry was measured, giving P_s values of about 20 nC cm^-2.     

Formation and reactivity of silacyclopropenes derived from siloxyalkynes: stereoselective formation of 1,2,4-triols

Silver phosphate-catalyzed silylene transfer to siloxyalkynes provided silacyclopropenes possessing a silyl enol ether functional group. Copper-catalyzed insertions of carbonyl compounds afforded the corresponding oxasilacyclopentenes. The embedded silyl enol ether functionality was treated with various aldehydes and a catalytic amount of Sc(OTf)3 to provide dioxasilacycloheptanones, which resulted from an aldol addition/rearrangement. Stereoselective reduction or allylation of the cyclic ketone, followed by n-Bu4NF deprotection, provided high yields of 1,2,4-triols possessing four contiguous stereocenters.     

Kinetic studies on the stability and reactivity of beta-amino alkylzinc iodides derived from amino acids

Beta-amino alkylzinc iodides are intrinsically unstable toward beta-elimination and protonation. The aim of this study was to determine the rates of these processes and also to understand how the reactivity of a range of beta-amino alkylzinc iodides in Negishi cross-coupling reactions is influenced by the presence of functional groups within the zinc reagent. Decomposition of beta-benzamido alkylzinc iodides occurs by protonation, and the first-order rate constant for the self-protonation of the carbon-zinc bond in reagent 4b was determined to be 5.2 x 10(-6) s(-1) (at 291 K). In contrast, the carbamate derivative 2 decomposes by a first-order elimination process. The homologous reagent 3, derived from glutamic acid, decomposes more quickly by beta-elimination, with a first-order rate constant of 24 x 10(-6) s(-1) (at 291 K). Reagents 23 and 25, in which the Boc group has been replaced with a trifluoroacetyl group, are more stable toward beta-elimination than the corresponding reagents 2 and 3, a striking outcome given that the trifluoroacetamido group is a better leaving group. Moreover, this replacement also changes the mechanism of the elimination to a second order process. Pseudo-second-order rate constants for the Negishi cross-coupling of reagents 2, 3, 23, and 25 with iodobenzene have been determined, revealing the higher reactivity of the glutamic acid-derived reagents 3 and 25. The main factor influencing reactivity, therefore, is determined to be the proximity of the ester group, rather than the nature of the nitrogen protecting group. Finally, beta-amino alkylzinc iodides 46-48 containing Weinreb amides have been prepared, rate constants for their decomposition through elimination determined, and their synthetic potential for the preparation of beta-amino ketones established.     

Changeable reactivity of ketyl radicals derived from 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones depending on electron transfer conditions employed

Photoinduced electron transfer reaction of 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols.     

Formation of carbon-carbon bonds with radicals derived from the esters of thiohydroxamic acids

Radicals formed from the esters of thiohydroxamic acids readily add to electron deficient olefins to give adducts of potential synthetic value in variable yield. In certain cases the added sulphur function is easily eliminated with reformation of olefin.     

Arylhydroxyacetic acids and amino acids derived from ethinylphenols

Conclusions A method of synthesis of arylhydroxyacetic acids and ammo acids derived from ethinylphenols has been developed in view of possible physiological activity of these compounds.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1170–1172, May, 1970.     

Stable frustrated phases in chiral liquid crystals derived from optically active (R)- and (S)-3-ethylmercapto-2-methylpropionic acids

Highly optically pure (R)- and (S)-3-ethylmercapto-2-methylpropionic acids were synthesized by using optically active (D)- and (L)-2,10-camphorsultams as chiral auxiliaries, respectively. Their derivatives, (R)- and (S)-EMMPNmB (m=6-12), were prepared for investigation. Microscopic texture observations demonstrated that the materials possess three stable frustrated phases: BP, TGB_A* and TGB_C* phases. Interestingly, it was found that the N* phase behaves as an intermediary phase between BP and TGB_A* phases in a rather narrow temperature range (calc. 0.5-1.4°C). A study of the racemic mixture, (±)-EMMPNmB (m=10), indicated that the chirality of the molecule could suppress the formation of smectic phases in the heating process. An increase of alkyl chain length favoured the formation of the TGB phases particularly, in accompaniment with a change of TGB phases from monotropic to enantiotropic. Moderate maximum P _S values (calc. 14-19 nC cm^-2) and apparent tilt angle (calc. 20°) were obtained for the TGB_C* phase in a surface stabilized ferroelectric liquid crystal geometry.     

Synthesis and reactivity of 3-(2-chloroalkyl)-2,2-dihaloaziridines

3-(2-Chloroalkyl)-2,2-dihaloaziridines were synthesized via cycloaddition of dihalocarbenes to the CN double bond of β-chloroimines. Under the action of Lewis acids or HCl, N-C³ bond cleavage occurred, giving rise to N-substituted 2,4-dichloro-3,3-dimethylbutanamides, which were further converted to 3-chloropyrrolidin-2-ones under alkaline conditions. When 2,2-dichloro-3-(2-chloro-1,1-dimethylethyl)-1-phenylaziridine was reacted with sodium methoxide, aziridine ring opening with N-C² bond cleavage took place, leading to methyl 4-chloro-3,3-dimethyl-2-(phenylamino)butanoate.     

Cidnp study of reactions of ketyls and dianions derived from benzophenone and fluorenone with acetic anhydride

A study is presented of ¹H and ¹³C CIDNP effects in the reactions of Na and Li salts of ketyls and dianions derived from benzophenone and fluorenone with acetic anhydride in tetrahydrofuran and dimethoxyethane. CIDNP effects were observed for products obtained by mixing of reactants both at high and at low field. Interpretation of the CIDNP effects (mixing at high field) indicates that in reactions of ketyls with acetic anhydride the primary step is O-acylation followed by spin-selective electron transfer between ketyl and O-acylated ketyl. At higher dilution or in the presence of strongly coordinating agents, heterolytic deprotonation of acetic anhydride by ketyl is also observed. CIDNP effects depend on the presence of ketyl which affects the relaxation of sterically accessible nuclei and also suppresses the intensity of ketone signals by rapid electron transfer. In reactions of dianions, electron transfer between dianion and acetic anhydride partly takes place, and the ketyl formed in this way reacts with a further molecule of acetic anhydride.     

Studies on pyrrolidones. Synthesis and reactivity of β-enaminomono-esters and β-enaminomononitriles derived from pyroglutamic acid

In the pyroglutamic acid series, β-enaminoesters 3 were formed in the 2-position by opening of the corresponding Meldrum's derivative 6 , and β-enaminonitriles 4 were obtained by treating carbamate vinylogous 5 by trimethytsilyl iodide. Alkylation and acylation of β-enaminoester 3a was briefly examined.     

Synthesis of new cationic and amphoteric triple-chain F-alkylated amphiphiles derived from 3-[N-[2-(F-alkyl)ethyl] N-alkylamino] propanoic acids

The N-[2-(F-alkyl)ethyl] amines were condensed with acrylic acid to afford the 3-[N-[2-(F-alkyl)ethyl] N-alkylamino] propanoic acids which are double-chain intermediates. To introduce a third chain, these intermediates and n-alkyl amines or n-2-(F-alkyl)ethyl amines were reacted according to three different methods to form triple-chain compounds which are quaternized by reagents such methyl iodide, ethyl bromoacetate and 1,3-propane sultone to form cationic and amphoteric triple-chain perfluoroalkylated surfactants.     

Fused hexacyclic tin compounds derived from 3-(3,5-di-t-butyl-2-hydroxy-phenylimino)-3H-phenoxazin-2-ol

The template synthesis of two tin compounds [N→Sn] 3-(2-oxo-phenylimino)-3H-phenoxazin-2-oxo-dimethyltin (1) and [N→Sn] 3-(2-oxo-phenylimino)-3H-phenoxazin-2-oxo-diphenyltin (2) is reported. The compounds are fused delocalized planar hexacyclic systems bearing a pentacoordinated diorganyl tin. They were identified by NMR, IR, TOF mass spectra and, for compound 1, by X-ray diffraction analysis.     

A new chiral oxazoline derived from camphor and its conversion to (R)-2-methylalkanoic acids

(1S,5R,7R)-(−)-10,10-Dimethyl-3-ethyl-4-oxa-2-azatricyclo[5.2.1.0^1,5]dec-2-ene 2 was prepared in 95% yield from (1S)-1-amino-2-exo-hydroxyapocamphane 1. The chiral oxazoline could be alkylated (LDA/THF/−78°C/RX, RX=ethyl, n-propyl, n-butyl iodides or benzyl bromide) to 3 in 95% yield and >95% diastereoselectivity, and the products hydrolysed to (R)-2-methylalkanoic acids 4 (43–47% yield, 93–98% e.e.).     

Protonation of 1,3- and 1,4-dinitrobenzene dianions

The protonation of the electrochemically generated (0.1 M solution of tetrabutylammonium perchlorate in DMF) 1,3-dinitrobenzene (1) dianions with phenol, ethanol, tert-butanol, and 1-butyl-3-methylimidazolium cation was studied by cyclic voltammetry and chronoamperometry at the carbositall working electrode. The rate constants for the protonation (k) of the dianion of compound 1 by phenol, 1-butyl-3-methylimidazolium cation, ethanol, and tert-butanol were estimated by the comparison of the data of cyclic voltammetry and chronoamperometry with the digital simulation results, being 100, 50, 1.5, and 0.01 L mol⁻¹ s⁻¹, respectively. The similarly obtained k value for the protonation of the dianion of 1,4-dinitrobenzene (2) with phenol is 13 L mol⁻¹ s⁻¹. According to the quantum chemical calculation results, the protonation of the dianions of compounds 1 and 2 with phenol and 1-butyl-3-methylimidazolium cation can be classified as orbital-controlled reactions. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1463–1466, July, 2008.     

Dual reactivity of diazonium salts derived from 1-amino-2-ethynyl-9,10-anthraquinones

Diazotization of vicinal 1-amino-2-ethynyl-4-R-9,10-anthraquinones followed by a reaction with NaN₃ gave 5-hydroxy-3-R-1H-naphtho[2,3-g]indazole-6,11-diones or 3-ethynyl-5-R-6H-anthra[1,9-cd]isoxazol-6-ones, depending on the substituents at the triply bonded C atom and in position 4 of the anthraquinone framework.     

Homo- and heterodimetallic geminal dianions derived from the bis(phosphinimine) {Ph2P(NSiMe3)}2CH2 and the alkali metals Li, Na, and K

The geminal organodimetallic complexes [({Ph2P(NSiMe3)}2C)2M4], where M4=Na4, 3; Li2Na2, 4; LiNa3, 5; Li2K2, 6; Na2K2, 7, and Na3K, 8, have been prepared through a variety of methods including direct or sequential deprotonation of the neutral ligand with strong bases (tBuLi, nBuNa, (Me3Si)2NNa, PhCH2K or (Me3Si)2NK), transmetalation of the homometallic derivatives (M4=Li4, 2 or Na4, 3) with tBuONa or tBuOK, and by cation exchange upon mixing the homometallic complexes in an arene solution. Complexes 3-8 have been characterized by single-crystal X-ray diffraction and are found to form a homologous series of dimeric structures in the solid-state, in accord with the previously reported structure of 2. Each complex is composed of a plane of four metals, M4, in which the ligands adopt capping positions to form distorted M4C2 octahedral cores. The metals in homometallic complexes 2 and 3 define an approximate square, whereas the heterometallic derivatives 4-8 have distinctly rhombic arrangements. The lighter metals in 4-8 interact strongly with the carbanions and the heavier metals are pushed towards the periphery of the structures. 1H, 13C, 7Li, 31P, and 29Si multinuclear NMR spectroscopic studies, cryoscopic measurements, and electrospray ionization-mass spectroscopic studies are consistent with the dimers being retained in solution. Dynamic solution behavior was discovered for Li2Na2 complex 4, in which all five possible tetrametallic derivatives Li4, Li3Na, Li2Na2, LiNa3 and Na4 coexist. Density functional theory (DFT) and natural bond order (NBO) calculations in association with natural population analyses (NPA) reveal significant differences in the electronic structures of the variously metalated dianions. The smaller cations are more effective in localizing the double negative charge on the carbanion (in the form of two lone pairs), leading to differences in the distribution of the electron density within the ligand backbones. In turn, a complex interplay of hyperconjugation, electrostatics and metal-ligand interactions is found to control the resulting electronic structures of the geminal organodimetallic complexes.