Proton affinity correlations between hydrogen and dihydrogen bond acceptors

Several series of hydrogen- and dihydrogen-bonded complexes with HCN, C2H2, HF, H2O, CH3CONH2, and CH3COOH as donors and H2O, MeOH, EtOH, MeOMe, NH3, NH2Me, NHMe2, NMe3, NEtMe2, and BH3-NMe3 as acceptors were investigated using the MP2/6-311++G(d,p) level of theory. The total lowering of the X-H stretching frequencies in the hydrogen-bonded complexes were linearly correlated with the proton affinities of the accepting bases. From comparison of hydrogen- and dihydrogen-bonded complexes, a scaling factor to estimate the exact proton affinity of a dihydrogen bond acceptor was developed. Further, the scaling factor involving linear donors (1.204) is marginally higher than that involving nonlinear donor molecules (1.162). Finally, it was found that, given identical conditions, a hydrogen bond will be about 16-20% stronger than a corresponding dihydrogen bond.     

Rh-catalyzed alkoxycarbonylation of unactivated alkyl chlorides

A general rhodium-catalyzed selective carbonylative coupling of unactivated alkyl chlorides with aliphatic alcohols or phenols to the corresponding esters is presented for the first time. Crucial for this transformation is the addition of sodium iodide, which provides in situ more active alkyl iodides. In the presence of a Rh(i)-DPPP catalyst system diverse esters (81 examples) including industrially relevant acetates from chloro- and dichloromethane can be prepared in a straightforward manner in up to 95% isolated yield. The used ligand not only affects the selectivity of the carbonylation reaction but also controls the selectivity of the preceding halide exchange step.

An efficient and convenient rhodium-catalyzed alkoxycarbonylation of unactivated alkyl chlorides was developed for the first time. More than 80 examples of esters were prepared directly from readily available substrates with often high selectivity.     

Vibrational analysis of tertiary alkyl chlorides

Vibrational spectra were obtained for 2-chloro-2-methylpentane, 3-chloro-3-methylpentane, 2-chloro-2-methylhexane, and 3-chloro-3-methylhexane. All four compounds exist in T_HHH and T_CHH conformations in the neat liquid, and the T_HHH' conformer of the last named compound also seems to be present. Only the T_HHH conformer is present in the crystalline state of the two pentanes, but the hexanes could not be made to crystallize and both conformers were present in the solid. A 44-parameter modified valence force field was used in normal coordinate calculations, with fifteen force constants being adjusted to fit 188 assigned frequencies below 1500 cm^?1 of six molecules (two conformers each of 2-chloro-2-methylbutane, 2-chloro-2-methylpentane, and 3-chloro-3-methylpentane). The resulting force constant values were used in zero-order calculations of the two hexanes as an aid in interpreting vibrational spectra for those compounds.     

Proton affinity of methyl nitrite and methyl peroxynitrite: implications for measuring branching ratios of alkyl nitrates and nitrites

Geometry optimizations for methyl nitrite and methyl peroxynitrite, along with various protonated isomers for each, have been investigated using ab initio and density functional methods. The lowest energy structure for protonated methyl nitrite is a complex between CH3OH and NO(+). For methyl peroxynitrite, the lowest energy protonated structure is a complex between CH3OOH and NO(+). Their respective proton affinities are estimated to be 195.2 and 195.8 kcal/mol at the QCISD(T)/6-311++G(3df,3pd) level of theory. The results, compared with past studies, suggest an alternative method for directly measuring branching ratios for production of alkyl nitrates and nitrites.     

Indium-catalyzed coupling reaction between silyl enolates and alkyl chlorides or alkyl ethers

The coupling reactions of alkyl chlorides with silyl enolates catalyzed by InBr₃, and the coupling reactions of alkyl ethers with silyl enolates catalyzed by the combined Lewis acid of InBr₃/Me₃SiBr are described. In both reaction systems, various types of silyl enolates were used to give corresponding α-alkylated esters, ketones, carboxylic acids, amides, thioesters, and aldehydes.     

Proton affinity of methyl peroxynitrate

The equilibrium structures, harmonic vibrational frequencies of methyl peroxynitrate, and structures of protonated methyl peroxynitrate have been investigated using ab initio methods. The methods include the single- and double-excitation quadratic configuration (QCISD) methods and the QCISD(T) method, which incorporates a perturbational estimate of the effects of corrected triple excitation. The lowest-energy gas-phase form of protonated methyl peroxynitrate is a complex between CH3OOH and NO2+. The CH3OOH.NO2+ complex is bound by 22 +/- 2 kcal/mol. The estimated proton affinity of methyl peroxynitrate is 178.8 +/- 3 kcal/mol. A general trend for the proton affinity of ROO-NO2 (peroxynitrates) compounds is discussed.     

Proton affinity of SO3

Collision-induced dissociation (CID) of the radical cation H₂SO₄⁺ gives the product pairs H₂O⁺+SO₃ and HO+HSO₃⁺ with a 1:3 ratio that is essentially independent of collision energy. Statistical analysis of the two channels indicates that the proton affinity of HO is 3±4 kJ/mol lower than that of SO₃. This can be used to derive PA(SO₃)=591±4 kJ/mol at 0 K and 596±4 kJ/mol at 298 K. Previously, Munson and Smith bracketed the proton affinity as PA(HBr)=584 kJ/mol<PA(SO₃)<PA(CO)=594 kJ/mol. The threshold of 152±16 kJ/mol for formation of H₂O⁺+SO₃ indicates that the barrier to CID is small or nonexistent, in contrast to the substantial barriers to decomposition for H₃SO₄⁺ and H₂SO₄.     

Alkylation of magnesium enamide with alkyl chlorides and fluorides

A magnesium enamide derived from N-2-(N',N'-diethylamino)ethyl imine reacts with a primary and secondary alkyl chloride or a primary alkyl fluoride to give an alpha-alkylated ketone in good to excellent yield after hydrolysis. The reaction takes place with a high level of inversion of stereochemistry at the electrophilic carbon center and will be useful for production of optically active compounds.     

Copolymers of vinyl and vinylidene chlorides with alkyl acrylates

High-molecular-weight copolymers of vinyl chloride and ethyl or butyl acrylate were prepared in high conversion and yield in the presence of boron trifluoride as the acrylate ester complexing agent. When the vinyl chloride monomer is in excess of equimolar amounts, the resulting copolymers are alternating; and when the alkyl acrylates are in excess, acrylate-rich copolymers are obtained. Ethylene–vinyl chloride–ethyl acrylate and propylene–vinyl chloride–ethyl acrylate terpolymers were also obtained with an ethyl acrylate content of 50 mole %. The relative reactivities of propylene, vinyl chloride, and ethylene in these polymerizations were 5.4, 3.8, and 1.0, respectively. Vinylidene chloride–ethyl acrylate copolymers that are nearly alternating and rich in acrylate or in vinylidene chloride have also been prepared. The monomer reactivity ratios for vinylidene chloride and ethyl acrylate in the presence of boron trifluoride are considerably lower than in its absence.     

Conversion of hydrazones to alkyl chlorides under Swern oxidation conditions

The unsubstituted hydrazones derived from aromatic ketones and aldehydes were converted in high yield to the corresponding alkyl chlorides under Swern oxidation conditions. In this unusual oxidation/reduction sequence the substrate undergoes a net reduction under the well established Swern oxidation conditions. Unsubstituted hydrazones derived from cyclohexyl ketones returned elimination products.     

Stereoconvergent amine-directed alkyl-alkyl Suzuki reactions of unactivated secondary alkyl chlorides

A new family of stereoconvergent cross-couplings of unactivated secondary alkyl electrophiles has been developed, specifically, arylamine-directed alkyl-alkyl Suzuki reactions. This represents the first such investigation to be focused on the use of alkyl chlorides as substrates. Structure-enantioselectivity studies are consistent with the nitrogen, not the aromatic ring, serving as the primary site of coordination of the arylamine to the catalyst. The rate law for this asymmetric cross-coupling is compatible with transmetalation being the turnover-limiting step of the catalytic cycle.     

Preparative synthesis of primary and secondary alkyl chlorides from alcohols

Conclusions We have developed a preparative single-stage tosylate method for obtaining chlorides from secondary and primary alcohols which isomerize when chlorinated by other methods.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2506–2508, November, 1987.     

A convenient preparation of glycosyl chlorides from aryl/alkyl thioglycosides

[reaction: see text]Because of the vast structural diversity encountered in the field of glycobiology, versatile methods for orthogonal oligosaccharide assembly are always of interest. Reported herein is the preparation of glycosyl chloride donors obtained by reaction of the corresponding thioglycoside precursors with chlorosulfonium chloride reagent 4. The crude chlorides thus obtained can be used directly in subsequent glycosylation reactions, and examples of the generality of this approach are provided.     

Photoacoustic measurements of multiple-photon infrared absorption by alkyl chlorides and hexadienes

The multiple-photon absorption behavior of a series of alkyl chlorides and a number of hexadiene isomers has been examined in order to elucidate the dependence of absorption cross section on fluence. Measurements of absorbed energy via a photoacoustic technique show that, while a high density of states is necessary for an absorption cross section linear in fluence, other factors are also important. A photoacoustic technique for measuring absorbed energy by weakly absorbing molecules at low pressure is described.     

A convenient one-pot Negishi coupling of amino-heteroaryl chlorides and alkyl bromides

A simple Ni-catalysed cross-coupling protocol for amino-heteroaryl chlorides with alkylzinc reagents has been developed. The alkylzinc reagents can be commercially available dialkylzincs or alkylzinc halides, or can be conveniently generated in situ from diethylzinc and primary alkyl bromides in the presence of the same inexpensive Ni catalyst used to effect the subsequent coupling reaction.     

Amino alcohols as ligands for nickel-catalyzed suzuki reactions of unactivated alkyl halides, including secondary alkyl chlorides, with arylboronic acids

Suzuki cross-coupling reactions of an unprecedented array of unactivated primary and secondary alkyl halides (including challenging alkyl chlorides) can be accomplished through the use of nickel/amino alcohol-based catalysts. Both the nickel precatalyst and the amino alcohols (prolinol or trans-2-aminocyclohexanol) are commercially available and air-stable. In view of the remarkable diversity of amino alcohols that are readily accessible, this discovery may open the door to the rapid development of versatile catalysts for a wide range of cross-coupling processes.     

NMP-mediated chlorination of aliphatic alcohols with aryl sulfonyl chloride for the synthesis of alkyl chlorides

NMP-mediated chlorination of aliphatic alcohols has been developed for the synthesis of alkyl chlorides. This facile, efficient and practical approach used simple and readily available aryl sulfonyl chlorides as the chlorination reagent for the construction of C–Cl bond in good to excellent yields with mild conditions and broad substrate scope.