Regioselective hydroborations of methylvinylchlorosilanes

The regioselectivity of the hydroboration of the methylchlorovinylsilanes, Cl_nMe_3?nSiCHCH₂ (n= 0 ? 3), has been investigated using BH₃←THF, 9-BBN, disiamyl- and dicyclohexylborane. Methylation of the adducts with methylmagnesium bromide is complicated by formation of tetraalkylboronates. Alkaline hydrogen peroxide oxidation of the boronates gives reasonable yields of the corresponding α- and β-trimethylsilylethanols forn= 0 and 1. Forn= 2 and 3, conversion of the adducts to the corresponding α- and β- deuteroethylsilanes by treatment with excess sodium methoxide in methanol-0-d provides a more effective means of derivatization. Addition of the alkenes,n= 2 or 3, to excess BH₃←THF givesca. 90% of the α-boro-organo-chlorosilanes. For all of the alkenes, the dialkylboranes giveca. 80% of the β-boron adducts.     

Synthesis of trans -N-2-aryl(heteryl)ethenamidines

2-Amino-2-arylethylamides1 carrying electron-donating substituents in thepara position are transformed by hot POC1₃ to the the title compounds2, presumably via iminochlorides 7 and imidazolium derivatives8. Amides lacking this para-substituent give rise to chloroamidines11 under these conditions.m-Methoxyphenethylamide1t and POCl₃ form, besides11f, an isoquinoline derivative3. The involvement of an imidazolium compound8 in the formation of ethenamidines has been verified by the synthesis of2a from10. Reaction of amide1w with PCl₅ in the cold leads to, besides the chloroamidine11c, thecis-ethenamidine12 which equilibrates with thetrans-isomer2o in hot toluene. Thienylethyl urea13 converted by hot POCl₃ to the imidazoline16, while phenylpropylamide17 forms only the iminochloride18a. Contribution No. 752 from Research Centre     

Study on the method of chemical trapping for formyl intermediates

The method of chemical trapping for formyl intermediates has been studied, with syngas conversion to ethanol over rhodium-based catalysts as the diagnostic reaction concerned, and CH₃I as the trapping reagent. Two species of acetaldehyde, i.e., CH₃CHO and CH₃CDO, were produced in the trapping reaction following CO + 2D₂ reaction. It was shown that the formation of CH₃CHO in the trapping reaction resulted from dehydrogenation of CH₃ from CH₃I to give H, which induced the formation of CH₃CHO in the presence of CO and CH₃ So there may be two pathways for the formation of CH₃CDO in the trapping reaction: one, methylation of DCO adspecies; the other, deuteration of CH₃ CO formed by CO insertion into CH₃ The catalyst surface was purged with Ar following CO + 2D₂ reaction before the trapping reaction was performed. By means of this modified method of chemical trapping for formyl intermediates, CH₃CDO was found to be mainly derived from the methylation of DCO adspecies. Accordingly, it could be concluded that formyl is a C₁ intermediate in the syngas conversion to ethanol over rhodium-based catalysts.     

Synthesis of 2-Aryl-1H-s-Triazolo[1, 5-a] Benzimidazoles

2-Aroylaminobenzimidazoles (2) have been converted into 1(2-benzimidazolyl)-5-aryl-1H-tetrazoles (4) by treatment with PCl₅ followed by azidation with NaN₃ in aqueous acetone solution. Pyrolysis of 4 in diphenylether yielded 2-aryl-1H-s-triazolo [1,5-a] benzimidazoles (6). The product of benzylation of 6a has been characterised. A reasonable pathway for the formation of 6 from 4 has been suggested.     

Proton lability in the amino ligand of and the1H-n.m.r. spectra oftrans-dichloro(diethylamine)(π-ethene)platinum and related complexes

Summary The NCH ₂CH₃ region of the¹H-n.m.r. spectrum oftrans-PtCl₂(-C₂H₄)(NHEt₂) has been investigated and shown to contain inequivalent protons. A study has also been made in related amine complexes of the conditions under which Pt-N-CH ₂ protons are equivalent, NH-CH coupling takes place and¹⁹⁵Pt-N-CH coupling occurs.The lability of the N-H bond intrans-olefin-amine, carbonyl-amine, ethanide-amine and phosphine-amine complexes is also investigated and compared with that of the platinum-amine link.Trans-labilizing powers of-C₂H₄, CO, CH₂¯CH₂ and Ph₃P are compared.     

Factors controlling electron transfer reactions and stabilisation of uncommon oxidation states of chromium

Some experimental approaches to seek semi-quantitative understanding of factors controlling outer sphere electron transfer reactions of some transition metal complexes have been made. The relative importance of nuclear and electronic factors to outer sphere processes has been examined. By the manipulation of Franck-Condon or nuclear factors, it has now been possible to gain access into the chemistry of chromium in unusual oxidation states. An example of a reorganisation controlled electron transfer reaction involving Cr(IV)-Cr(III) system has been demonstrated. The bimolecular rate of reduction of diperoxoaquaethylenediamine chromium(IV) and diperoxodiethylenetriamine chromium(IV) is independent of the nature of th reductant employed viz. Fe²⁺ or VO²⁺ indicating that the generation of6 coordinate Cr(IV) species from7 coordinate of diperoxochromium(IV) reactant may be rate limiting. Similarly by increasing the barrier for the6 coordinate to4 coordinate structures through equatorial coordination of macrocyclic ligands, it has now been possible to detect through cyclic voltommogram the formation of relatively stable Cr(IV) species in the electrochemical oxidation of Cr(Me₄[14] tetraene)(H₂O) ₂ ³⁺ in aqueous sulphuric acid media. The kinetics and mechanism of the cerium(IV) and iodosyl benzene oxidation of Cr(salen)(H₂O) ₂ ⁺ and Cr(salprn)(H₂O) ₂ ⁺ have been investigated and kinetic and spectroscopic evidence for the formation of Cr(IV) transients and stable Cr(V) products has been presented. The relative importance of Franck-Condon factors in the oxidation of Cr(III) to Cr(IV) and Cr(V) states in different macrocyclic and multidentate ligand environments has been discussed.     

Synthesis and crystal structure of Na2CaP2O7

Na₂CaP₂O₇ has been prepared in single crystal form by fusion techniques. The single crystal structure: a = 5.361(3), b = 7.029(3), c = 8.743(4)Å, α = 69.40(2), β = 89.02(3), γ = 88.78(4) °, V = 308.5(3)ų, space group P1 bar, Z = 2, D_calc = 2.799 mg/m³, R/R_w = 0.0445/0.0554 for 1434 observed reflections (F>4.0σ(F), shows a solid state form similar to that of K₂SrP₂O₇, K₂MnP₂O₇ and KaCdP₂O₇.     

Synthesis and structure of hexakis (p-hydroxyphenyloxy)benzene: A versatile analogue of the hydrogen-bonded hexameric unit of β-hydroquinone

The title hexaphenol (1), a direct analogue of the -hydroquinone hexameric unit, has been prepared by six-fold demethylation of hexakis (p-methoxyphenyloxy)benzene (2) with BBr₃. Host1 forms a trigonal adduct, space groupR3,a=22.088(3),c=12.232(3) Å, containing 6 molecules of pyridine per host molecule: a detailed X-ray study of this inclusion compound reveals a true clathrate structure, the closed cages of which accommodate a small, non-stoichiometric amount of water.     

Investigation of Aconite alkaloids

Summary The composition of the alkaloids in plants of the genus Aconitum —A. kirinense,A. altaicum, A. coreanum, andA. nemorosum — has been studied. Four new alkaloids of composition C₂₆H₄₁O₈N·HNO₃, C₃₅H₄₁O₁₀N·HBr, C₂₀H₂₅O₃N, and C₂₃H₂₉O₆N have been isolated.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 2, pp. 113–116, 1965.     

A highly stereoselective pinacolization of aromatic and α, β-unsaturated aldehydes.dta mediated by titanium(III)-magnesium(II) complex

Reduction of Cp₂TiCl₂ withsec-BuMgCl in THF gave a greenish deep brown solution which has been found to promote the reductive homocoupling of aromatic and α, β-unsaturated aldehydes to yield symmetrical 1, 2-diols with highthreo-selectivity.     

Triterpenoids from Rhododendron caucasicum and Rh. ledebourii gas-liquid chromatography of rhododendron extracts

Conclusions FromGentiana olgae have been isolated gentiananine, gentianadine, and the new base gentianaine C₆H₇O₃N. The structural formula for the latter has been given.G. caucasica contains gentianine and gentiananine; andG. kaufmanniana contains gentianine, gentianaine, and gentiananine; gentianaine has been found in the mother liquors fromG. turkestanorum andG. olivieri.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 1, pp. 32–36, 1969     

20-ISO-20-Deethylaspidospermidine

The two-step process of hydrogenation of l-alkyl-3-acylpyridinium salts and cyclization of the resultant 1, 4, 5, 6-tetrahydropyridines has been the foundation of a general scheme of alkaloid synthesis.¹ Its application in the indole alkaloid field has yielded ready access to tetrahydro-β-carboline systems, e.g. 1a → 2 → eburnamonine.² Since acid treatment of N_b -acyl derivatives of substances related to la has been shown to lead to products of indole β-cyclization³, it became of interest to test the cyclization behavior of the vinylogous imide lb, prepared by the dicyclohexylcarbodiimide-induced acylation of 3-acetyl-1, 4, 5, 6-tetrahydropyridine⁴ with indoleacetic acid. Treatment of lb with boron trifluoride gave a 62 yield of ketolactam 3a. Thus a two-step entry into the pentacyclic Aspidosperma alkaloid skeleton is on hand.     

Methylaluminum complexes based on tridentate 2,6-bis(mercaptoalkyl)pyridine SNS-ligands

New SNS-ligands were obtained by consequent ring-opening of substituted thiiranes by lithiated 2,6-lutidine, mono- functionalized SN-ligands having been isolated as the intermediate compounds. The molecular structure of ligand 2,6-Py(CH₂CH₂CBn₂SH)₂ was elucidated by XRD analysis.The reaction of AlMe₃ with SNS-ligands afforded monomeric methyl aluminum complexes which have been tested in ring- opening polymerization of ε caprolactone in bulk.     

Novel Mild Synthesis of N-Carboxylotriphenylphosphin-Imines & Id N-Amidotriphenylphosphinimines VIA Ligand Exchange Processes in Dichlorotriphenylphosphine

Abstract

In connection with our recent investigations on the ligand exchange processes in five-coordinated phosphoranes and phosphonium salts a new, one-pot synthesis of various N-carboxylotriphenylphosphinimines 1 and N-amidotriphenylphosphinimines 2 has been devised. The key intermediate, phosphonium salt 4, was obtained in quantitative yield by the reaction of Ph₃PCl₂ with cyanate salts Pb(OCN)₂ and NaOCN. When alcohols or amines were present, salt 4 was converted into 1 and 2:     

Synthesis of natural triisopentenylated flavanone, euchrenone a2

Euchrenone a₂ (7) isolated from the roots ofEuchresta japonica has been synthesised from 3-prenylphloroacetophenone (1) by other workers. We carried out its cyclodehydrogenation with dichloro dicyano quinone (DDQ) to obtain 6-acetyl-5,7-dihydroxy-2,2-dimethylchromene (2) which was ethoxymethylated in the 7-position to give 6-acetyl-7-ethoxymethoxy-5-hydroxychromene (3). Chalcone condensation of3 and 4-ethoxymethoxy-3-C-prenylbenzaldehyde (4) gave 4,6′-bisethoxymethoxy-2′-hydroxy-6″, 6″-dimethyl-3-C-prenylpyrano (2″, 3″–4,3) chalcone (5) which cyclised with methanolic sodium acetate to give protected 5,4′-bisethoxymethoxy-6″, 6″-dimethyl-3′-C-prenylpyrano (2″, 3″–7,8) flavanone (6). Deprotection of6 with 4% methanolic HCl yielded (7) with melting point and spectral data identical to that of the natural compound.     

Anomalous1H NMR spectra of 3,4-dihydroisoquinolines and related compounds

Solutions of 3,4-dihydro-6,7-methylenedioxyisoquinoline (1) and analogues2–5 and9 as well as isoquinolines7 and8 in certain samples of CDCl₃, CCl₄, DMSO-d₆ or acetone-d₆ gave rise to anomalous¹Hnmr spectra with extreme line broadening, signals due to protons at C-l and C-3 most often not being seen. The spectra of1 and3 were most striking in this respect.¹Hnmr spectra of the quaternary salt10 and the model schiff base11 were normal. Several hypotheses for the observed line broadening have been considered and rejected, a slow equilibrium1 ⇆13 being one of them. NaBH₄ reduction of1 and2 followed by mass spectrometric analysis of the crude tetrahydroisoquinolines16 and17 ruled out a slow equilibrium1 ⇆14 and2 ⇆15 as contributory cause for line broadening. The crude reduction products unexpectedly contained N-ethyl species22 and25. Their formation is rationalised     

Hydroformylation of olefins catalyzed by rhodium complex anchored on clay matrices

Investigations on the catalytic activity of a transient Rh(I) triphenylphosphine complex1 anchored on montmorillonite clay have been carried out with respect to hydroformylation of olefins at 70°C and 60 atm of CO+H₂ (1:1). The analysis has shown that aldehydes and hydrocarbons of the corresponding olefins result under hydroformylation conditions. In limonene, reaction proceeds with double hydroformylation and hydrogenation to give the respective oxo products. The catalytic activities of1 are compared with Wilkinson's Rh^I (H) (CO) (PPh₃)₂ (6) complex in solution under the same hydroformylation conditions.     

The structure of vincarine

Summary A new base, vincarine, has been isolated from the roots and epigeal part ofV. erecta. Its formula is C₂₁H₂₄O₃N₂.The structure of vincarine has been established by analysis of the UV, IR, NMR, and mass spectra and also by its conversion into polyneuridine; it is a diastereoisomer of quebrachidine.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 2, pp. 110–113, 1965.     

A Facile Synthesis of 2-Aminonicotinaldehyde

A synthesis of 2-aminonicotinaldehyde (1) which does not require chromatography and is easily scaled up has been developed. Bromination of 2-amino-3-picoline, protected as a phthalimide (4), produced the gem-dibromide (5), which was reacted with Nh₄OH. The imine intermediate (7) was hydrolyzed with acid, producing (1) in a 56% conversion from 4.