Alkyl Isocyanates Research Articles

Tin for Organic Synthesis, 11. A Mild and Effective Synthesis of α,β‐unsaturated Carboxamides and Sulfonamides by Electrophilic Substitution of Alkenylstannanes with Isocyanates

AbstractA new and effective method for the preparation of a variety of olefinic carboxamides 6a–k and N‐(4‐methylphenyl‐sulfonyl) carboxamides 7a–d is described. The reaction of aryl and alkyl isocyanates 4a–c or 4‐methylphenylsulfonyl isocyanate 5 with 1‐alkenyltrialkylstannanes 1a–e and di‐1‐alkenyldibutylstannanes 2a–c in the presence of aluminium trichloride provides the corresponding N‐aryl‐substituted olefinic carboxamides 6a–k or the N‐(4‐methylphenyl‐sulfonyl)‐substituted olefinic carboxamides 7a–d in good yields. The stannyl moiety is superior to hydrogen as a leaving group and enables electrophilic ipso substitution at the vinylic system. In the case of di‐1‐alkenyldibutylstannanes the substitutions are also stereospecific, whereas the reactions of 1‐alkenyltrialkylstannanes with isocyanates proceed with partial isomerisation.

Helix reversals as bad neighbors to liquid crystal organizations in cholesteric states and thermally reversible gels of poly(ALKYL isocyanates)

AbstractWhile the temperature dependence of the lyotropic cholesteric pitch of the single helical sense poly ((R)‐2,6‐dimethylheptyl isocyanate) is in line with theory, comparable data on this state produced by chiral doping of the lyotropic nematic state of poly(n‐hexyl isocyanate) could suggest an interplay between the supramolecular chirality of the liquid crystal and the dynamic equilibrium of the left and right hand helical blocks in this otherwise racemic polyisocyanate. The exclusion of helix reversals, as undersireable kinks in the liquid crystal organization, could play a role in this effect. Such helix reversal exclusions can also explain the peculiar chiral optical changes associated with the thermally reversible gelation of poly(n‐hexyl isocyanate) copolymers in hydrocarbon solvents. These gels likely arise by entering the broad biphasic region of the Flory phase diagram leading to the formation of liquid crystal aggregates.

1,2-Carbon to nitrogen migrations. Part 2. Ab initio study on the rearrangement of (α-methylazo)alkyl isocyanates

Ab initio molecular orbital calculations have been employed to study the rearrangement of (α-methylazo)alkyl isocyanates to 1,2,5-trisubstituted 1,2-dihydro-1,2,4-triazol-3-ones. The migration of three different substituents (methyl, ethyl and isopropyl) has been investigated. Geometries of stationary points on the potential energy hypersurface were optimized at the HF/6-31G* level of theory. Second order Moeller Plesset perturbation theory with the 6-31G* basis set was applied in order to correct for correlation effects. Selected geometries were reoptimized at the MP2/6-31G* level. HF/6-31G*, MP2/6-31G*//HF/6-31G* and MP2/6-31G* energies predict migratory aptitudes in the order isopropyl > ethyl > methyl. In the transition states, partial charges obtained from natural population analysis indicate strong electron deficiency at the nitrogen atom being the target for migration. The transition states show partial carbocation character of the migrating group with respect to charge distribution and geometry. An alternative reaction pathway, namely 1,2-shift of a methyl group to the adjacent nitrogen of the isocyanato function leading to formation of 2,4,5-trimethyl-2,4-dihydro-1,2,4-triazol-3-one, has been investigated, but can be excluded due to the much higher activation energy required.

Reaction of Tetrahydro-b-carboline-1-carboxylic Acid with Isocyanates and Isothiocynates. Synthesis of 1-Alkyl- or Arkylcarbomoyl-b-carbolines

The reaction of (±)-1,2,3,4-tetrahydro-β-carboline-1-carboxylic acid (8) with alkyl and aryl isocyanates formed the corresponding tetrahydro- β-carboline-hydantoin ring systems (7). However the reaction of (8) with isothiocyanates provided 2-alkyl- or arylthiocarbamoyl-1,2,3,4-te- trahydro-β-carbolines (9). The oxidation of (7) with selenium dioxide or dichlorodicyano-p-benzoquinone gave 1-substituted β-carbolines (10) related to β-carboline alkaloids

Versatile Organometallic Initiators for the Living Polymerization of Isocyanates

Shashoua and Sweeney first demonstrated that isocyanates could by polymerized via an anionic mechanism to form high molecular weight materials. We have sought to eliminate the problems associated with the anionic procedure by developing transition metal complexes which are capable of catalyzing the living polymerization of isocyanates. Recently, we reported the living polymerization of alkyl isocyanates using TiCl3OCH2CF3, I. Using I, polyisocyanates with controlled molecular weights and narrow polydispersities can be obtained at room temperature. e5-CpTiCl2N(CH3)2 (Cp = cyclopentadienyl), III, is also an excellent catalyst for the polymerization of isocyanates, and in terms of ease of handling and purification and tolerance toward monomer functionality, superior to I. In order to prepare triblock copolymers containing amorphous segments sandwiched between two isocyanate segments, we have prepared bimetallic initiators comprised of titanium alkoxides con- nected by flexible linkers. These linkers may be a...

Cooperativity and chirality in a wormlike helical macromolecule

AbstractA question about broken rods and worms concerning the dimensional characteristics of poly(alkyl isocyanates) led to the discovery of an extreme sensitivity of this polymer class to tiny chiral perturbations. There is a cooperative source of this phenomenon and statistical thermodynamic methods allow quantitative expression to the forces at work. From this effort we could answer the original question and also extend these ideas into the area of lyotropic liquid crystals where the interplay of macromolecular and supramolecular helicity seems to play by the same rules.

Eburnane‐14‐spiro heterocycles. Synthesis and stereostructure determination by NMR spectroscopy

AbstractNew spiroheterocyclic systems, eburnane‐14‐spiro‐5′‐oxazolidinedione, eburnane‐14‐spiro‐4′‐imidazolidinedione and related compounds were prepared by reacting vincamine stereoisomers or 14‐desoxy‐14‐aminovincamines with alkyl isocyanates. Stereostructures of the new compounds were proved by 1H and 13C NMR spectroscopy, including DR, DNOE, DEPT and 2D HSC measurements.

Well‐defined polyisocyanates via organotitanium(IV) catalyzed living polymerizations of isocyanates

AbstractThe development of living organotitanium(IV) catalyzed polymerizations is presented. A living polymerization of alkyl isocyanates was developed using TiCl3OCH2CF3, I, as a catalyst, through which large quantities of well‐defined (in terms of molecular weight and polydispersity) polyisocyanates are obtainable under ambient conditions. η5‐CpTiCl2OCH2CF3 (Cp = cyclopentadienyl), II, is also an excellent catalyst for the polymerization of isocyanates and, unlike I, will polymerize monomers containing Lewis basic functional groups in the side chain. Compound II was used to synthesize poly(allyl isocyanate) and poly(2‐isocyanatoethyl methacrylate). Both polymers were found to be soluble, in contrast to previous reports, and spectroscopic characterization showed that no crosslinking of the side chains had occurred.

Synthesis, structure, and carbamoylation of 5-alkyl-N(1)-(?-hydroxyethyl)-4,5-dihydro-1,2,4-triazin-6-ones

The condensation of methyl α-(dimethylaminomethyleneamino)alkanoates with β-hydroxyethylhydrazine gave the isomeric N(1)- and N(2)-(β-hydroxyethyl)-5-alkyl-4,5-dihydro-1,2,4-triazin-6-ones. It was shown by IR spectroscopy that the products exist in the form of betaines both in solution and in the crystalline state. The reaction of the N(1) isomers with alkyl and aryl isocyanates leads to the formation of mono- or dicarbamoyl-substituted triazines. The preferred reaction path involves carbamoylation of the β-hydroxyethyl group.

Helical conformations, internal motion, and helix sense reversal in polyisocyanates and the preferred helix sense of an optically active polyisocyanate

Empirical force field studies of poly(alkyl isocyanates) are presented. A barrier of 12.5 kcal/mol for cis-trans isomerization of the polymer-backbone's conjugated partial double bonds makes the calculated energy of helix sense reversal agree best with corresponding experimental results. The alternating cis and trans torsion angles are found to be distorted, to about 170° and -55° for right-handed helices, by strong repulsions between the α-carbon of each alkylside chain and the neighboring backbone atoms of four consecutive monomer units

Vibrational Study of Alkyl Isocyanates in Solution

The vasym. NCO frequencies for alkyl isocyanates occur at higher frequency in CHCl3 solution than in CCl4 solution. With the exception of tert-butyl isocyanate, the vasym. NCO mode increases in frequency as the mole % CHCl3/CCl4 increases. The vasym. NCO mode for tert-butyl analog increases in frequency up to a certain mole % CHCl3/CCl4 and then vasym. NCO decreases in frequency. The vasym. NCO mode for n-butyl isocyanate occurs at an exceptionally high frequency for the alkyl isocyanate studied, and this result is explained in terms of the formation of a pseudo six-membered intermolecular hydrogen-bonded ring. Inductive and steric factors also influence the type and form of solvent/solute complexes formed vs. mole % CHCl3/CCl4 as determined by study of the vasym. NCC frequencies. In general, the vasym. NCO and the vsym. NCO modes for alky isocyanates decrease in frequency as the number of hydrogen atoms on the α-carbon atom of the alkyl group decreases from 3, to 2, to 1, to 0. Some of the alkyl isocyanates exhibit two significant IR bands in the region expected for vasym. NCO, and the methyl analog exhibits three significant bands in this region of the spectrum. These IR bands are the result of vasym. NCO in Fermi resonance with combination tones, and the unperturbed frequencies have been calculated with the use of the recorded data.

IR and NMR Correlations for Alkyl Isocyanates

Correlations are presented for υasym.NCO vs. δ(13C) for NCO, δ13C for NCO vs. the number of protons on the alkyl α-carbon atom, and υasym.NCO vs. the number of protons on the alkyl α-carbon atom for alkyl isocyanates. Correlations such as these are useful in the elucidation of unknown molecular structures containing the isocyanate group.

1,4,4a,10b-Tetrahydro-N,N-dimethyl-4-phenanthridinamines and 1,4,4a,5,6,10b-hexahydro-N,N-dimethyl-4-phenanthridinamines

Synthetic procedures to prepare the title compounds are described. Diels-Alder cycloaddition of β-nitrostyrene derivatives 5 to N,N-dimethyl-1,3-butadien-1-amine, 6, gave 5-aryl-N,N-dimethyl-6-nitro-2-cyclohexen-1-amines 7. Reduction of 7 with zinc in acetic acid gave the diamino derivatives 8. Schotten-Baumann acylation of 8 gave amides 9. Treatment of 8 with alkyl isocyanates gave the aminourea derivatives 10. Bischler-Napieralski cyclodehydration procudure of 9 and 10 gave 1,4,4a,10b-tetrahydrophenanthridinamines 3 and N6-alkyl-1,4,4a,10b-tetrahydro-N4,N4-dimethyl-4,6-phenanthridinediamines 11, respectively. Condensation of diamines 8 with aryl aldehydes under azeotropic conditions gave imines 12 which on treatment with acids yielded 6-aryl-1,4,4a,5,6,10b-hexahydro-N,N-dimethyl-4-phenanthridinamines 4. The stereochemistry of these materials is assigned from the proton magnetic resonance studies.

ChemInform Abstract: Synthetic Methods and Reactions. Part 148. Preparation of Tertiary Alkyl Isocyanates by the Zinc Iodide Catalyzed Reaction of Tertiary Alkanoyl Chlorides with Trimethylsilyl Azide.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

A Convenient and General Synthesis of Alkylcarbamates from Tertiary Isocyanates and Alcohols

Reaction of primary, secondary and tertiary alkyl isocyanates with benzyl alcohol, tert-butyl alcohol or 1-adamantanol in the presence of 5% hydrogen chloride provides a mild and convenient method for alkyl alkylcarbamate synthesis

Notes. Synthesis and crystal structures of [PPh4][MN{ButNC(O)NBut}Cl2](M = Ru or Os); a new reaction of tert-butyl isocyanate. Synthesis of W[ButNC(O)NBut]2(NHBut)2

The interaction of the tetraphenylphosphonium salts of the ruthenium- and osmium-(VI) anions [RuO2Cl3]–, [RuO2Cl4]2– and [OsO2Cl4]2– with excess of tert-butyl isocyanate in acetonitrile forms the salts of the anions [MN{ButNC(O)NBut}Cl2]–, M = Ru or Os. X-Ray diffraction studies have shown the anions to have distorted square-pyramidal geometry with nitrido groups in axial positions. The metal nitrido groups have been shown to arise by C–N bond cleavage of unisolated tert-butylimido intermediates accompanied by cycloelimination of Me2CCH2 and HCl. Similar reactions using other aryl and alkyl isocyanates gave intractable products. The compound W[ButNC(O)NBut]2(NHBut)2 is formed on reaction of W(NBut)2(NHBut)2 with ButNCO.

ChemInform Abstract: Selective Monocarbamoylation of Symmetrical Diols with Alkyl Halides and Potassium Cyanate Using Phase‐Transfer Catalysis.

AbstractReaction of aliphatic diols such as (I) with alkyl isocyanates, generated in situ from alkyl halides such as (II) and potassium cyanate (III) under phase‐transfer conditions, yields the monourethane (IV).

Unambiguous structure of the compounds in the reaction of L‐tryptophan and 5‐hydroxy‐l‐tryptophan with alkyl isocyanates in acetone

AbstractOn the basis of X‐ray crystallographic analysis, it is shown that the reaction of L‐tryptophan and 5‐hydroxy‐L‐tryptophan with alkyl isocyanates in acetone affords, in agreement with Claesson's work, 3‐alkylcarbamoyl‐4‐(3‐indolylmethyl)‐1,3‐oxazolidin‐5‐ones 2 and not 2‐[(3‐alkyl‐4,4‐dimethyl‐2‐oxo)‐1,3‐diazetidinyl]‐3‐(3‐indolyl)propionic acids 1 as previously proposed.

Synthetic methods and reactions. Part 148. Preparation of tertiary alkyl isocyanates by the zinc iodide catalyzed reaction of tertiary alkanoyl chlorides with trimethylsilyl azide

Des cyclo(polycyclo)alkyl isocyanates tertiaires ont ete prepares avec un rendement sensiblement quantitatif par une reaction entre des chlorures d'alcools tertiaires et de l'azoture de trimethylsylyle, catalysee par l'iodure de zinc. En comparaison, la reaction des halogenures d'alkyles tertiaires avec l'isocyanate de trimethylsylyle en presence d'acides de Lewis comme le SnCl 4 donne seulement les isocyanates correspondants avec un faible rendement de synthese

Syntheses with Hypophosphorous Acid and its Derivatives

Abstract The interaction of hypophosphorous acid and its salts with hydroxyl-containing compounds:alkyl halids, isocyanates, formaldehydes and amines was investigated. The new polyfunctional phosphonous acids were obtained.