First Long-Distance SRN1 on a propargylic chloride

We report here the first example of a Long-Distance S_RN1 (LD-S_RN1) reaction on a propargylic chloride. The reaction of 1-(3-chloroprop-1-ynyl)-4-nitrobenzene (1) with nitronate anions led to both the formation of the C-alkylation product through an LD-S_RN1 mechanism and the ethylenic compound resulting from nitrous acid elimination on the C-alkylation product 2. In contrast with previous work on LD-S_RN1 reactivity, no O-alkylation product was observed. Only one original product 4 was isolated under phase transfer conditions, resulting from a nucleophilic attack by 2-nitropropane anion on the electrophilic alkyne. This LD-S_RN1 reactivity did not extend to sulfinate anions; the reaction of 1 with sulfinate anions yielded original ethylenic disulfone compounds which were formed via an ionic process.     

Novel fluoropolymers formed by an unprecedented SRN1 condensation polymerization mechanism

A condensation copolymerization reaction between bis-phenol A and p-bis-(chlorodifluoro-methyl)benzene has been carried out to form a novel fluoropolymer that has excellent thermal and solubility properties. It is proposed that this polymerization reaction occurs via an unprecedented S_RN1 mechanism. This demonstration of the use of S_RN1 chemistry for condensation polymerizations of fluorinated monomers creates the opportunity for preparation of new fluoropolymers which are otherwise inaccessible.     

A novel example of vinylic SRN1: Reactions of 3,3-difluoro-1-iodo-2-phenylcyclopropene with thiolate ions

The reactions of 3,3-difluoro-1-iodo-2-phenylcyclopropene with thiolate ions (with a molar ratio of 1:1) were carried out in laboratory illumination to give the corresponding substituted product. The presence of p-dinitrobenzene (p-DNB) or hydroquinone (HQ) as well as darkness significantly suppressed the reaction. ESR trapping experiments also evidenced the existence of fluorinated radical. All these results demonstrate the reaction involved a vinylic saturated alkyl and aromatic halides (S_RN1) mechanism.     

A novel SRN1 substitution: the reaction between the anion of 2-nitropropane and 3-bromo-1-nitrocyclohex-1-ene

X-Ray crystallography has been used to determine the unusual cyclopropyl structure for the product of the S_RNl reaction between the anion of 2-nitropropane and 3-bromo-1-nitrocyclohex-1-ene.     

Synthesis of cyclohexadienylstannanes - Novel example of vinylic SRN1 mechanism: A theoretical and experimental study

The reaction of trimethyltinsodium (1) with 1-(diethoxyphosphoryl)oxy-1,3-cyclohexadienes in liquid ammonia under irradiation affords the corresponding 1-trimethylstannylcyclohexadienes. We suggest that these reactions occur by an S_RN1 mechanism. On the other hand, 2-(diethoxyphosphoryl)oxy-1,3-cyclohexadiene reacts very slowly towards 1 and the substitution product decomposes under the reaction conditions employed. Thus, structurally similar compounds do not behave in the same way under ET conditions. We suggest that this behavior is mainly due to differences in spin density of their radical anions, which affect their fragmentation rates. Our results are supported by computational calculations.     

Syntheses of phenanthridines and benzophenanthridines by intramolecular ortho-arylation of aryl amide ions with aryl halides via SRN1 reactions

The photostimulated reaction of N-(2-halo-benzyl)aryl amines with t-BuOK in liquid ammonia affords fused azaheterocycles by the S_RN1 mechanism. The starting materials are easily obtained by the reaction of 2-halo-benzyl chloride and aromatic amines to prepare the secondary amines. Through this approach, phenanthridine (90%), 4-phenylphenanthridine (87%), benzo[a]phenanthridine (98%), and benzo[c]phenanthridine (84%) were synthesized.     

Selective synthesis of mono- and distannylpyridines from chloropyridinols via an SRN1 mechanism

A selective two-step synthesis of either mono- or distannylated pyridines from commercially available pyridinols, involving its conversion to the corresponding diethyl pyridyl phosphates (pyDEP) followed by the reaction with Me₃SnNa in liquid ammonia, is described.The results obtained clearly indicate that the reactions proceed through an unimolecular radical nucleophilic substitution mechanism (S_RN1) with intermediacy of a monosubstitution product.     

Synthesis of 2‐substituted‐3‐nitroimidazo[1,2‐b]pyridazines as potential biologically active agents

A new heterocyclic reductive alkylating agent, 6‐chloro‐2‐chloromethyl‐3‐nitroimidazo[1,2‐b]pyridazine, was synthesized for the first time. It was shown to react under phase‐transfer catalysis conditions with 2‐nitropropane anion by an S_RN1 mechanism to give excellent yield of isopropylidene derivative formed from a base‐promoted nitrous acid elimination of C‐alkylation product. Extension of this S_RN1 reaction to various nitronate anions led to a new class of 3‐nitroimidazo[1,2‐b]pyridazine derivatives bearing a trisub‐stituted double bond at the 2‐position.     

Photostimulated reactions of haloarenes with 2-naphtylamide ions. A facile synthesis of 1-aryl-2-naphthylamines.

The photostimulated reactions of aryl iodides with 2-naphthylamide ions in liquid ammonia gave 1-aryl-2-naphthylamines as the major substitution product. This reaction is proposed to occur by the S_RN1 mechanism of nucleophilic substitution     

Steric and electronic limitations of the SRN1 reaction between p-nitrobenzylic substrates and tertiary carbanions

The S_RN1 reaction between sterically hindered p-nitrobenzylic substrates and tertiary carbanions gives C-alkylated products whose yields depend on the steric bulk of both the benzylic substrate and the carbanion, and on the nature of the groups in the carbanion.     

<Emphasis Type="Italic">S</Emphasis><Subscript>RN</Subscript>1 Reactions in the Nitrobenzo[1,3]dioxole Series

5-Chloromethyl-6-nitrobenzo[1,3]dioxole has been shown to react with 2-nitropropane anion to give C-alkylation by an S _RN1 mechanism. The reaction was extended to various aliphatic, cyclic, and heterocyclic nitronate anions, leading to a new series of nitrobenzo[1,3]dioxole derivatives.     

Etude stereochimique de l'alkylation d'anions par des derives p-nitrobenzyliques optiquement actifs : Competition SN2-SNR1

Competition between S_RN1,S_N2 and S_RN1 mechanisms is discussed according to the stereochemical results in the alkylation of anions by optically active secondary p-nitrobenzyl reagents. Results from alkylation of the anions of benzylcyanide C and α-aminonitrile A by p-nitrobenzyl chloride 2 rule out S_N2 and S_RN2 mechanisms. On the other hand, the S_N2 process becomes exclusive in O-and C-alkylation of the acetoacetic ester anion B by the p-nitrobenzyl phosphonium salt, and this result shows that it is possible to obtain p-nitrobenzyl alkylation products without racemisation. C-Alkylation of the anion B by halide 2 involves an S_N2-electron transfer competition. The whole result illustrates that the stereochemical method provides precise information on the mechanism of these reactions.     

Coupling of iodonaphthalenes with naphthoxide ions under SRN1 conditions. Synthesis of unsymmetrical binaphthyl derivatives.

Unsymmetrical 1,1′-, 1,2′- and 2,2′-binaphthyl derivatives are obtained by a one-step coupling reaction of variously substituted moieties: naphthoxides and iodonaphthalenes; an S_RN1 mechanism is proposed.     

Studies on SRN1 reactions-9 : A new access to the isoquinoline ring system

The S_RN1 reaction between o-halogeno-benzylamines and enolates derived from a series of ketones and aldehydes affords 1, 2 dihydro-isoquinolines from which are obtained (i)the isoquinoline derivatives, either spontaneously or by treatment on Pd-C and (ii) the 1,2,3,4 tetrahydro-isoquinoline derivatives after sodium borohydride reduction.     

A novel synthesis of spiro[(2,2-dimethyl-[1,3]-dioxane)-5,2′-(2′,3′-dihydroindole)] using SRN1 reaction conditions

A concise synthesis of the spiro[(2,2-dimethyl-[1,3]-dioxane)-5,2′-(2′,3′-dihydroindole)] nucleus from substituted benzyl chlorides and 5-(hydroxymethyl)-2,2-dimethyl-5-nitro-1,3-dioxane 5 as starting materials is reported. The nitro intermediates 6 and 7 were prepared under S_RN1 reaction conditions.     

Photo-SRN1 reactions of phenyl telluride anion with haloarenes

Phenyl telluride anion was prepared in liquid ammonia by reaction of dipheyyl ditelluride with two equivalents of sodium metal under nitrogen. This anion reacts with haloarenes under irradiation to form aryl phenyl tellurides, probably by the photo-S_RN1 mechanism of aromatic substitution.     

The SON2 mechanism : A non-oxidative reaction that is initiated by electron transfer oxidation

Under oxidizing conditions, aromatic chloro and fluoro compounds undergo what formally are typical nucleophilic substitution reactions with surprising ease. As an example, 4-fluoroanisole is converted the 4-acetoxyanisole by anodic or metal ion oxidative initiation, and the reaction is shown to be a chain process. It is proposed that a mechanism analogous to that of the reductively initiated S_RN1 mechanism operates: The substrate is oxidized to a radical cation by the initiator system, and the radical cation then undergoes ipso attack by the nucleophile. In the third step, the leaving group leaves as a species at the same oxidation level as the nucleophile, giving the radical cation of the product to be formed. A chain transfer step involving this ion and a new substrate molecule then completes the propagation sequence.Previously reported cases of this phenomenon are discussed and the individual steps of the chain reaction are considered in terms of their thermochemistry. It is concluded that the S_ON2 mechanism should be more favoured with easily oxidizable substrates.     

Study of the reactivity of ketone enolates with 3-halo-2-amino derivatives of benzo[b]thiophene under photostimulated sRN1 reaction conditions

Reactivity of the 3-halo-2-amino derivatives of benzo[6]thiophene 1a-c and 2 with several ketone enolates 3–5 have been studied under photostimulated S_RN1 reaction conditions. The normal substitution product 6 only was obtained in low yields using potassioacetophenone 3 as the enolate ion and 2-(tert-butoxycarbonylamino)-3-chlorobenzo[b]thiophene ( 1a ) and 2-(tert-butoxycarbonylamino)-3-iodobenzo[b]thiophene ( 1c ) as substrates. In all reactions the main product was the corresponding dehalogenated substrate 7a-b , thus indicating that reduction of the substrate strongly competes with the desired substitution reaction.     

Effects of methanol solvation on the nucleophilic reactions of thiolates with 2-substituted-2-nitropropanes

Methanol solvation prevents S_RN1 substitution in the reaction of Me₂C(X)NO₂ with thiolates and favours an alternative redox reaction to yield disulphide and nitronate.     

Nouvelle synthèse du squelette dihydro-1,2 isoquinoléine par réaction de substitution nucléophile radicalaire en chaìne (SRN1)

The S_RN1 reaction between ortho-iodo-benzylamine and ketone enolates affords the 1,2-dihydroisoquinoline ring system from which the 3-substituted isoquinolines or the 1,2,3,4- tetrahydroisoquinoline are obtaines.