Nucleophilic addition of nitriles to tertiary monocyclic terpenes alcohols

Previously unknown secondary amines have been synthesized by the Ritter reaction of p-menthan-8-ol with propio- and benzonitriles. The performance of this reaction with -terpeneol and benzonitrile led to the formation of a mixture of N-(p-menth-1-en-8-yl)benzamide and N,N-(p-menth-1,8-diyl)dibenzamide. A transdiamide was also obtained on the reaction of -terpineol with isovaleronitrile. The use of propionitrile as the nucleophile with -terpineol led to the formation of 2-ethyl-4,4,8-trimethyl-8-propionamido-3-azabicyclo[3.3.1]non-2-ene.Institute of Physical Organic Chemistry, Academy of Sciences of the Belorussian SSR, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 235–240, March–April, 1987.     

The diastereospecific aprotic conjugate addition reactions of allylic anions-mechanistic aspects.

A ten-membered cyclic “chair-chair” - or “$\text{trans}$-decalyl”-like TS is proposed to account for the diastereospecific aprotic conjugate addition reactions of allylic carbanions bearing polar, charge-stabilizing groups.     

The diastereospecific aprotic conjugate addition reactions of carbanions derived from allylic sulfoxides and allylic phosphine oxides.

The title carbanions undergo conjugate addition to cyclic enones in THF to deliver vinylic sulfoxides and vinylic phosphine oxides as single diastereomers.     

Nucleophilic identity substitution reactions. The reaction between water and protonated alcohols

The potential energy surfaces for the reaction between H2O and the protonated alcohols MeOH2+, EtOH2+, PriOH2+, and Bu(t)OH2+ have been explored by means of high level ab initio theoretical methods. Both nucleophilic substitution (SN2) and elimination (E2) pathways have been investigated. Front side (SNF) and the familiar back side (SNB) Walden inversion attack of the nucleophile have been found to be competing for the H2O Bu(t)OH2+ system. In contradiction with the customary relationship between so-called "steric effects" and barrier heights--more alkyl-substituted SN2 reaction centres have higher SN2 reaction barriers--the SN2 reaction barriers are found to be Et > Me > Pri > Bui. This result is in excellent agreement with available experimental data.     

Nucleophilic addition of water to coordinated dipyridylethylene in rhenium(V) complexes

Complexes of general formula [ReOX₂{(C₅H₄N)CH(O)CH₂(C₅H₄N)}] (X?=?Cl,?I) were prepared by reaction of trans-[ReOCl₃(PPh₃)₂] and trans-[ReOI₂(OEt)(PPh₃)₂] with cis-1,2-di-(2-pyridyl)ethylene (DPE) in ethanol and benzene in air. The coordinated DPE ligand undergoes addition of water at the ethylenic carbon atoms, and the (C₅H₄N)CH(O)CH₂(C₅H₄N) moiety acts as a uninegative terdentate N,O,N-donor ligand. X-ray crystal structures of both complexes have been determined and show distorted octahedral geometry at the rhenium(V) centre.     

Use of ion-molecule reactions and methanol addition to improve arsenic determination in high chlorine food samples by DRC-ICP-MS

Direct determination of trace arsenic in high chlorine food samples by ICP-MS is complicated by the presence of ArCl⁺ interferences, and the high first ionization energy of As (9.81 eV) also results in low analytical sensitivity in ICP-MS. In this work, two strategies based on ion-molecule reactions were successfully used to eliminate ArCl spectral interference in a dynamic reaction cell (DRC). The interference ion (⁴⁰Ar³⁵Cl⁺) was directly removed by the reaction with methane gas, and the background signal was reduced by up to 100-fold at m/z 75. Alternatively, by using molecule oxygen as the reaction gas, ⁷⁵As⁺ was effectively converted to ⁷⁵As¹⁶O⁺ that could be detected at m/z 91 where the background is low. The poor signal intensity of As or AsO was improved 3-4 times by addition of 4% methanol in the analyzed solutions. The limit of quantitation (LOQ) for ⁷⁵As (CH₄-DRC method) and ⁷⁵As¹⁶O (O₂-DRC method) was 0.8 and 0.3 ng g⁻¹ and the analytical results of seaweed and yellow croaker standard reference materials were in good agreement with the certified values. As the routine arsenic monitoring method in our laboratory, it was applied to the accuracy determination of 119 high chlorine food samples from eight different markets of Beijing.     

A theoretical study of S(N)2' reactions of allylic halides: role of ion pairs

Various disparate experimental results are explained by the hypothesis that reactions of anionic nucleophiles with allylic halides are generally S(N)2. The S(N)2' reactions that do occur proceed generally with anti stereochemistry. Reactions with ion pair nucleophiles occur preferentially as S(N)2' reactions with syn stereochemistry. This hypothesis is consistent with a variety of computations at the HF, B3LYP, mPW1PW91 and MP2 levels with the 6-31+G(d) basis set of reactions of Li and Na fluoride and chloride with allyl halides and 4-halo-2-pentenes. Solvation is considered by a combination of coordination of dimethyl ether to the lithium and sodium cations and "dielectric solvation" with a polarized continuum model.     

Nucleophilic displacement reactions on fluorine. II. The role of σ- and π-bond nucleophiles

S_N2 displacement reactions on fluorine by σ- and π-bond nucleophiles are discussed and shown to constitute a general class of reaction. Mechanisms are suggested for reactions mentioned in the literature which are consistent with this generalization.     

Diastereoselective addition of gamma-substituted allylic nucleophiles to ketones: highly stereoselective synthesis of tertiary homoallylic alcohols using an allylic tributylstannane/stannous chloride system

The diastereoselective addition of gamma-substituted allylic nucleophiles to ketones has been accomplished to give tertiary homoallylic alcohols. The reaction of tributylcinnamyltin 1a with simple ketones 2 in the presence of stannous chloride (SnCl(2)) gave the tertiary homoallylic alcohols 3, which include the anti form (based on Ph and OH), with high diastereoselectivity. In the reaction course, transmetalation of tributylcinnamyltin 1a with SnCl(2) proceeds to form an active nucleophile which is tentatively considered to be a cinnamyltin(II) species. A cyclic transition state A is favorable because the chlorinated tin(II) center is highly capable of accepting ligands. The other diastereomers (syn form) 4 were obtained in the reaction of tributylcinnamyltin 1a with ketones 2 by the use of BF(3) x OEt(2) instead of SnCl(2). This reaction proceeds through an acyclic transition state in which BF(3) acts as a Lewis acid for activation of ketones. When 3-tributylstannylcyclohexene 1b or 3-tributylstannylcyclopentene 1c was used with SnCl(2), high diastereoselective formation of the corresponding homoallylic alcohols 6 which have the syn form (based on ring chain and OH) was observed. The selectivity was also explained by the cyclic transition state B. When tributylcrotyltin 1d or 1e was used, the stereochemistry of the products depends on the additives (SnCl(2) or BF(3) x OEt(2)), substituents of ketones, and reaction temperature. It is interesting that those additives compensate for each other in terms of diastereoselective alkylation. The alkylation of alpha-alkoxy, aryloxy, or hydroxyketones 16 was achieved in extremely high selectivity using an allylic tributyltin 1a-c/SnCl(2) system. The chelation by carbonyl and beta-oxygens provides a rigid transition state (E or F) for selective reactions. It is noted that the hydroxyketone can be used without protection in this reaction system. The relative stereochemistry of the produced tertiary homoallylic alcohols was determined on the basis of X-ray analyses.     

Nucleophilic behavior of DBU in a conjugate addition reaction

Reaction of DBU with a diarylpyrone results in 1,4 addition of the DBU and subsequent fragmentation of the DBU moiety into an aminopropyl caprolactam. Incorporation of the fragmented DBU into the diarylpyridone is postulated to occur by an addition/elimination pathway.     

Nucleophilic addition to acetylenes in superbasic catalytic systems. 12. Vinylation of lupinine

The addition of a natural alkaloid lupinine to acetylene in the presence of superbasic catalytic systems (KOH—DMSO, KOBu^t—DMSO, KOH—dioxane) under elevated or atmospheric pressure affords O-vinyllupinine (in up to 88% yield), a promising optically active monomer and intermediate for the preparation of new quinolizidine alkaloids. The same vinyl ether was obtained (in 60% yield) by the reaction of lupinine with vinyl acetate in the presence of Hg(OAc)₂.     

The role of intramolecular hydrogen bonds in nucleophilic addition reactions of ketenaminals

Quantum-chemical calculations of the geometries and electronic structures of molecules of ketenaminals 3-(diaminomethylene)-2,4-pentanedione and dimethyl-2-(diaminomethylene)-malonate and calculations of the structures of intermediates in the reaction of the nucleophilic addition of the ketenaminals to the acetonitrile molecule are performed by B3LYP/6-31+G** method. Two possible scenarios of the process are shown, depending on the mutual orientation of reacting molecules. The nucleophilic addition proceeds in two stages. It is found that the rate-limiting stage of the process is the transfer of the proton of the intramolecular hydrogen bond in a ketenaminal molecule. The experimentally observed faster reaction of pyrimidine formation for the 3-(diaminomethylene)-2,4-pentanedione molecule relative to that for dimethyl-2-(diaminomethylene)-malonate is explained by the hydrogen bond being stronger and the barrier of proton transfer from the aminogroup to the ketogroup oxygen falling upon nucleophilic attack in the former molecule.     

The role of noninnocent solvent molecules in organocatalyzed asymmetric Michael addition reactions

A proline-catalyzed asymmetric Michael addition between ketones and trans-beta-nitrostyrene was studied by using the density-functional theory with mPW1PW91 and B3LYP functionals. Improved insight into the enantio- and diastereoselective formation of gamma-nitroketones/-aldehydes is obtained through transition-state analysis. Consideration of the activation parameters obtained from gas-phase calculations and continuum solvation models failed to reproduce the reported experimental stereoselectivities for the reaction between cyclohexanone and 3-pentanone with trans-beta-nitrostyrene. The correct diastereo- and enantioselectivites were obtained only upon explicit inclusion of solvent molecules in the diastereomeric transition states that pertain to the C--C bond formation. Among the several transition-state models that were examined, the one that exhibits cooperative hydrogen-bonding interactions with two molecules of methanol could explain the correct stereochemical outcome of the Michael reaction. The change in differential stabilization that arises as a result of electrostatic and hydrogen-bonding interactions in the key transition states is identified as the contributing factor toward obtaining the correct diastereomer. This study establishes the importance of including explicit solvent molecules in situations in which the gas-phase and continuum models are inadequate in obtaining meaningful insight regarding experimental stereoselectivities.     

Nucleophilic addition of phosphine to 4-chlorostyrenes in the KOH-DMSO system

In the superbasic system KOH-DMSO (H₂O) at 60–75 °C (2–2.5 h, atmospheric pressure), 4-chlorostyrene and 4-chloro-α-methylstyrene add phosphine at the double bond to form 1: 1 and 2: 1 anti-Markovnikov adducts in 10–18% and 58–67% yields, respectively.