Vinyl Migration Research Articles

P(NMe2)3-Mediated Reductive Intramolecular Annulation of Benzoylformates Tethered with a Trisubstituted Alkene Unit and Synthesis of 2,2-Disubstituted 2H-Chromenes.

In this report, a P(NMe2)3-mediated reductive intramolecular annulation reaction has been developed with benzoyl formates bearing a trisubstituted alkene unit. It provides a facile synthesis of highly functionalized 2,2-disubstituted 2H-chromenes with a broad substrate scope and high efficiency. Experimental results suggest this annulation reaction proceeds via a cascade of alkene isomerization/vinyl o-quinone methide formation/6π-electrocyclization. As a key intermediate, the vinyl-substituted o-quinone methide is presumably generated by a Kukhtin-Ramirez adduct initiated O → C vinyl migration.

Regioselective introduction of vinyl trifluoromethylthioether to remote unactivated C(sp3)—H bonds via radical translocation cascade

Described herein is an efficient protocol for the regioselective introduction of a vinyl trifluoromethylthioether to remote unactivated C(sp3)–H bonds. The cascade process involves the vinyl radical-mediated 1,5-hydrogen atom transfer (HAT) and remote vinyl migration. During the transformation, inert C–H and C–C bonds are consecutively cleaved under mild conditions. The reaction features good functional group tolerance, broad substrate scope, and high regio-/stereo-selectivity.

Wagner–Meerwein rearrangement of [3.3.1] bicyclic N-Boc aminols: vinyl migration in preference to aryl migration

The Wagner–Meerwein rearrangement of [3.3.1] bicyclic N-Boc aminols was established, featuring the migration of the vinyl group instead of the aromatic ring. The structure of the rearrangement product was deduced through extensive spectroscopic studies and confirmed by the synthetic efforts. The scope of the reaction was examined and reasonably good yields were obtained for substrates with alkyl, allyl or benzyl substituent.

Development of a dynamic headspace - capillary GC - MS method for the determination of ultra-trace levels of vinyl chloride in water samples and during migration studies

A method based on automated dynamic headspace sampling followed by thermal desorption – capillary GC – MS was developed to monitor ultratraces of vinyl chloride in water samples. The method shows excellent performance including a limit of quantification (LOQ) below 10 ng/L, good linearity (r2 > 0.999) in the 10 to 200 ng/L concentration range and an RSD below 10% at all calibration levels. The method was applied to study the release of traces of vinyl chloride monomer (VCM) in water from aged polyvinyl chloride (PVC) pipes installed in water supply systems. A solution to avoid this leaching would be the insertion of a polyethylene pipe inside the PVC pipe provided that vinyl chloride does not permeate through polyethylene. Vinyl chloride migration through a high density polyethylene (HDPE) film was therefore studied with the developed sampling method.

Synthesis and Mass Spectral Studies of Some (E)- and (Z)-1-Alkylthio - and 1-Alkylsulphonyl-2-P-Tolylsulphonylstilbenes

A number of (E)- and (Z)-1-alkylthio-2-p-tolylsulphonylstilbenes (3a–i and 5a–i) were synthesized by the nucleophilic displacement of halogens with sodium salts of various alkanethiols on (E)-1-chloro-2-p-tolylsulphonylstilbene (1) and (Z)-1-bromo-2-p-tolylsulphonylstilbene (2) respectively. Oxidation of these (E) - and (Z)-1-alkylthio-2-p-tolylsulphonyl gave the corresponding (E)- and (Z)-1-alkylsulphonyl-2-p-tolylsulphonylstilbenes (4a–i and 6a–i) respectively. Mass spectral data of all the synthesized compounds were examined. Smiles-type rearrangement observed in (E)-and (Z)- sulphide-sulphones (3a–i and 5a–i) was absent in (E)- and (Z)-disulphones (4a–i and 6a–i). Loss of sulphur dioxide and sulphonyl-sulphinate rearrangement with vinyl migration was noticed in all the synthesized compounds. McLafferty-type rearrangement was observed only in (E)- sulphide-sulphones and (E)- disulphones but not in the corresponding (Z)-isomers.

The carbonyl insertion reaction of ethylCo(CO) n(PH 3) 4− n and vinylCo(CO) n(PH 3) 4− n: A detailed DFT study

A DFT study on CO insertion into Co-ethyl and Co-vinyl is carried out comprehensively. All structures are optimized completely and the mechanism of the CO insertion is discussed in detail. These CO insertion processes of ethylCo(CO) n (PH 3) 4− n and vinylCo(CO) n (PH 3) 4− n ( n=1–4) are actually alkyl migration onto carbonyl. The entropy does not play a critical role in the ethyl and vinyl migration. The computational results indicate that CO insertion into sp 2-C is easier than the CO insertion into sp 3-C from the view of kinetics except for the three-PH 3-ligand-substituted system. It attributes to the interaction between the 3d orbital of Co and π orbital of vinyl, possibly. Transition sates of all processes occur late on potential energy surface and the transition states of vinyl migration occur later than ethyl migration.

Mechanism of novel consecutive rearrangements of cyclobutene-fused diphenylhomobenzoquinones catalyzed by lewis acids.

Lewis acid catalyzed rearrangements of highly strained [2 + 2] photoadducts 1a-d of diphenylhomobenzoquinone with various acetylenes were investigated under the influence of AlCl(3), SnCl(4), BF(3), and TiCl(4). With the relief of steric strain, these tricyclo[5.2.0.0(3,5)]non-8-ene-2,6-diones underwent the three steps of consecutive skeletal transformations. The first step was the two-way cyclobutene ring-cleavage reaction with a Wagner-Meerwein vinyl migration to either Lewis acid activated carbonyl function. This process virtually occurred under the anchimeric assistance of the endo-phenyl ring to give, after proton transfer, the phenylene-bridged tetracyclic keto alcohols 2 and 3, respectively. The next step was the acid-induced cyclopropane ring cleavage of only 3 to lead to bicyclic diones 4 via a following stereoselective proton transfer. The last one involved a Michael-type intramolecular cyclization of 4 accompanied by a proton transfer to afford thermodynamically less stable tricyclic diones 5alpha which epimerized to 5beta only by TiCl(4). The factors that control the selectivity and the reactivity of these tandem reactions were addressed on the basis of the X-ray crystal analyses as well as the PM3 calculations. It was found the present Lewis acid-catalyzed rearrangements were very dependent on the substituents of 1a-d and the nature of the Lewis acids.

The beckmann rearrangement of cyclohex‐2‐enone oximes. Synthesis of 4,5‐diphenyl‐2,3,4,5‐tetrahydro‐1H‐azepin‐2‐one

AbstractThe Beckmann rearrangement of either syn or anti 3,4‐diphenyl‐cyclohexenone oxime 2a,b in polyphosphoric acid produces only one of the two possible isomeric unsaturated caprolactams 1. Under neutral conditions, only the syn oxime tosylate 9b rearranges to lactam 1, the anti oxime tosylate 9a remains unchanged. These results support earlier reports that alkyl migration is preferred over vinyl migration in the Beckmann rearrangement of unsaturated cyclic ketoximes. Structure proof of the lactam was made using deuterium exchange and HMQC nmr experiments.

Control of the migratory aptitudes of vinyl and aryl ligands in ruthenium(II) complexes

Complexes Ru(CO) 2 (CH=CHR) (C 6 H 4 X-4)L 2 (R= t Bu, Ph, OEt; X=H, Cl, OMe; L=PMe 3 , PMe 2 Ph, P(OMe) 2 Ph) in which the two phosphorus ligands are mutually cis (isomer 1 ) react readily with ligands t BuNC, CO and P(OMe) 3 to give complexes in which one of the organic ligands has migrated onto a carbonyl ligand. Vinyl migration products ( 5 ) retain the mutually cis geometry of the phosphorus ligands, and are unstable: one of the decomposition products is the ketone RCH=CHC(O)C 6 H 4 X-4. Phenyl migration products ( 4 ) are stable and have the phosphorus ligands in mutually trans positions; an X-ray crystal structure of Ru(CO) (CN t Bu) {C(O)Ph} (CH=CHPh) (PMe 2 Ph) 2 was obtained. In both cases, the incoming ligand enters trans to the newly formed acyl ligand. Vinyl migration is favoured over aryl migration by electron-donating substituents on the vinyl ligand, electron-withdrawing substituents on the aryl ligand, good σ-donor phosphorus ligands and use of t BuNC as the incoming ligand. The rate of phenyl migration in Ru(CO) 2 (CH=CHPh)Ph(PMe 2 Ph) 2 is independent of t BuNC concentration: k =1.5 × 10 −3 s −1 at 20°C. Isomer 3 of complexes Ru(CO) 2 (CH=CHR) (C 6 H 4 X-4)L 2 in which the phosphorus ligands are mutually trans is much less reactive towards migration reactions. The reactivity of isomer 1 is attributed to the steric strain of two mutually cis phosphorus ligands.

SYNTHESIS AND MASS SPECTRAL REARRANGEMENTS OF SOME NEW MIXED VINYL SULPHIDE-SULPHONES AND DISULPHONES

Abstract Stererospecifically prepared (E)-1-chloro-2-p-chlorophenylsulphonylstilbene (1) and (Z)-1-bromo-2-p-chlorophenylsulphonylstilbene (6) on reaction with sodium alkyl thiolates in abs. ethanol underwent nucleophilic displacement of halogens leading to the formation of (E)- and (Z)-1-alkylsulphenyl-2-p-chlorophenylsulphonylstilbenes (2 and 7). The sulphide-sulphones 2 and 7 on oxidation afforded the corresponding disulphones (3 and 8). Mass spectra of (E)- and (Z)-isomers of 1-butylsulphenyl-2-p-chlorophenylsulphonylstilbenes (2c and 7c) and their corresponding disulphones 3c and 8c are examined at 70 eV. Smiles type rearrangement is noticed only in 2c and 7c but not in 3c and 8c. McLafferty type rearrangement involving migration of hydrogen from aryl and/or alkyl groups to ethylenic carbon is observed both in sulphide-sulphones and in disulphones. Sulphonyl-sulphinate rearrangement with vinyl migration as the predominant pathway is a noted feature in both sulphide-sulphones and disulphones.

SYNTHESES AND MASS SPECTRAL REARRANGEMENTS OF UNSATURATED BIS-SULPHIDES AND BIS-SULPHONES

Abstract The synthesis of (E)- and (Z)-1.2-bis(p-fluorophenylsulphenyl)stilbenes (2a and 2b) and 1,2-bis(p-fluorophenylsulphonyl)stilbenes (3a and 3b) was carried out and their configurations were consistent with their stereospecific synthesis. The isomeric 1,1-bis(p-fluorophenylsulphenyl)- and 1,1-bis(p-fluorophenylsulphonyl)-2,2-bis(phenyl)ethylenes (8 and 9) were also synthesised and configurations were established by degradative oxidation. Mass spectral rearrangements of all these compounds were examined. Mass spectra of 1,1-bis-sulphide and 1,1-bis-sulphone bears close relationship with those of (E)- and (Z)-isomeric counterparts. Smiles-type rearrangement observed in 1,2-bis-sulphides was absent in 1,2-bis-sulphones. McLafferty-type rearrangement involving hydrogen migration, from aryl group was noticed in both bis-sulphides and bis-sulphones. Vinyl migration to the sulphone oxygen predominates over aryl migration in three isomeric bis-sulphones.

ChemInform Abstract: Beckmann Rearrangement of δ4‐6‐Hydroxyimino Steroids.

Beckmann rearrangement of Δ4-6-hydroxyimino steroids gave solely the products of vinyl migration. Compounds having a 3-hydroxy or 3-acetoxy group suffer elimination of the substituent during the reaction.

Beckmann rearrangement of Δ4-6-hydroxyimino steroids

Beckmann rearrangement of Δ4-6-hydroxyimino steroids gave solely the products of vinyl migration. Compounds having a 3-hydroxy or 3-acetoxy group suffer elimination of the substituent during the reaction.

Some photochemical rearrangements of vinylcyclopentadienes. Mechanistic and exploratory organic photochemistry

The photochemistry of 2,3-diphenyl-1,4,5-trimethyl-5-vinylcyclopentadiene and 1,2-diphenyl-3,4,5-trimethyl-5-vinylcyclopentadiene was studied. The triplet of the 2,3-diphenyl isomer was found to undergo a 1,5-vinyl migration; in contrast, the 1,2-diphenyl diene was unreactive. On direct irradiation, in addition to vinyl migration, four photoproducts were formed from the cyclopentadienes. These were shown to be 5,6-diphenyl-1,2,7-trimethylbicyclo[3.2.0]hepta-2,6-diene, 1,5-diphenyl-2,6,7-trimethylbicyclo[3.2.0]hepta-2,6-diene, 6,7-diphenyl-1,2,5-trimethylbicyclo[3.2.0]hepta-2,6-diene, and 1,7-diphenyl-2,5,6-trimethylbicyclo[3.2.0]hepta-2,6-diene. A number of experimental observations led to a mechanism involving: (a) electrocyclic closure of the vinylcyclopentadienes to give vinyl housenes, (b) bicycling which interconverts isomeric housenes, and (c) thermal Cope rearrangement of the vinyl housenes to afford bicyclo[3.2.0]hepta-2,6-dienes. In addition, evidence was adduced for 1,5-vinyl shifts occurring in the vinylcyclopentadiene reactants.

VINYL MIGRATION IN THE OXYTHALLATION OF SOME 1,3-DIENES

Abstract The oxythallation of certain 1,3-dienes with thallium(III) nitrate trihydrate in MeOH–CH2Cl2 at 0–20 °C gave products after vinyl migration. Methyl 1-methylcyclopropyl ketone, obtained in the reaction of 2,3-dimethyl-1,3-butadiene, was presumably derived from a cyclopropylmethyl cation, an intermediate in the vinyl migration.

Stereochemistry of concerted 1,2-vinyl migration to a developing carbenium-ion centre

The first example of the stereochemistry of vinyl migration employing an optically active substrate is reported; the parallel behaviour between 1,2-migration of a vinyl group and a carbonyl group, under otherwise identical conditions, provides additional evidence for the concept of neighbouring group participation at carbonyl carbon in 1,2-acyl migrations.

The mass spectral rearrangements of aryl propenyl sulfones. An electron impact induced smiles type rearrangement

AbstractThe mass spectral behavior of trans‐1‐arylsulfonyl‐2‐arylsulfenyl‐propenes, trans‐1‐arylsulfonyl‐2‐arylsulfinyl‐propenes and trans‐1, 2‐(arylsulfonyl)‐propenes was examined. A Smiles type rearrangement was present in the sulfonyl‐sulfides, but was completely absent in the trans‐1‐arylsulfonyl‐2‐arylsulfinyl‐propenes and trans‐1, 2‐(arylsulfonyl)‐propenes. Vinyl migration to the sulfone oxygen predominates over aryl migration in all of the compounds studied. The mass spectra of the cis and trans isomers of 1‐p‐tolylsulfenyl‐2‐p′‐tolysulfonyl‐propene and 1, 2‐(p‐tolylsulfonyl)‐propene are also described.

Vinyl group migration and formation of spirocyclopropanes on treatment of 9-ethyl vinyl ethers of xanthene, thioxanthene and N-methyl acridan with base

Vinyl group migration and formation of spirocyclopropanes on treatment of 9-ethyl vinyl ethers of xanthene, thioxanthene and N-methyl acridan with base

Photochemical reactions. VI. Photo‐Beckmann rearrangement with vinyl migration. Preliminary communication

AbstractThe carefully controlled UV. irradiation of 3‐hydroxyimino‐Δ4‐ and 3‐hydroxyimino‐Δ4, Δ6‐steroids yield as a result of vinyl and alkyl migration, lactams besides products expected.

ChemInform Abstract: THE BEHAVIOR OF THIOCHROMANONE AND ISOTHIOCHROMANONE SULFOXIDES IN THE SCHMIDT REACTION, ISOLATION OF A NOVEL AZIDE PRODUCT FROM THIOCHROMONE SULFONE

AbstractDie Thiochromanono.xide (I) bzw. (III) liefern bei der Schmidt‐Reaktion je ein einziges Lactam (II) bzw. (IV); im Gegensatz dazu gibt das Analoge (V) die Isomeren (VI) und (VII).