Anionic Rearrangement Research Articles

ChemInform Abstract: 1,2 Anionic Rearrangements in the Gas Phase. The (Acyloxy)acetate- Acylhydroxyacetate and Related Rearrangements.

ChemInform 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.

ChemInform Abstract: The Complex Anionic Rearrangements of Deprotonated α-Oximino Carbonyl Derivatives in the Gas Phase

α-Oximino ketones R1COC(NOH)R2 deprotonate preferentially to form R1COC(NO–)R2 and this anion decomposes by a variety of complex rearrangement processes. The two major fragmentations involve the following overall processes (i) and (ii). (i) R1COC(NO–)R2 [graphic omitted] R1CO2–+ R2CN, and (ii) R1COC(NO–)CH2R [graphic omitted] –O(R1)CCCH2+ RNO(R = H or alkyl) It is proposed that reaction (i) involves a four-centre reaction of O– at the carbonyl carbon. No evidence of a Beckmann-type rearrangement is indicated for α-oximino ketones. The corresponding deprotonated α-oximino ketone O-methyl ethers also fragment by complex rearrangement. For example, MeCOC(NOMe)Me deprotonates to form two ions which are interconvertible on collisional activation. The enolate ion is the principal deprotonated species, and it decomposes by the overall process –CH2COC(NOMe)Me →–CH2CN + CH2CO + MeOH. The other anion decomposes by loss of methanol. This is best rationalised either by the Beckmann process MeCOC(NOMe)CH2–→[(CH2CNCOMe)MeO–]→ CH2CNCOCH2–+ MeOH, or a related Neber rearrangement. This investigation was aided by deuterium labelling, and product ion studies.

ChemInform Abstract: Anionic Fries Rearrangements of Esters of ortho-Iodobenzyl Alcohols: Rapid Routes to Oestrone Methyl Ether and Its 9β-Epimer, and Aryl Naphthalide Lignans.

A fast, general, low-temperature rearrangement of ortho-iodobenzyl esters, triggered by lithium–iodine exchange, leads to isobenzofurans which are intercepted in situ by inter and intramolecular Diels–Alder (IMDA) reactions to produce a variety of carbocycles including natural lignans and steroids.

ChemInform Abstract: Directed ortho-Metalation of O-Aryl and O-Pyridyl Thiocarbamates. A Versatile Synthetic Method for Substituted Phenol into Thiophenol Conversion.

The preparation of ortho-substituted O-aryl and O-pyrid-3-yl thiocarbamates 7a-h and 11a-d and anionic ortho-Fries rearrangements of selected cases, [O-phenyl N,N-diethylthiocarbamate (6a)→N,N-diethyl-2-hydroxy-3-methylbenzenecarbothioamide (9), 0-[4-(trimethylsilyl)pyridyl-3-yl] N,N-diethylthiocarbamate (11a)→N,N-diethyl-3-hydroxy-4-(trimethylsilyl)pyridine-3-carbothioamide (13)], via the directed ortho metalation protocol are described

ChemInform Abstract: High Asymmetric Induction in Anionic Amino-Cope Rearrangements Controlled by β-Aminoalcohol Auxiliaries.

ChemInform Abstract: High Asymmetric Induction in Anionic Amino-Cope Rearrangements Controlled by β-Aminoalcohol Auxiliaries.

ChemInform Abstract: Catalytic Conjugate Addition Promoted by the Copper(I) Monothiobinaphthol System. Part 3. Comparison of Three Thiolate-Based Catalytic Systems.

Monothiobinaphthol (MTB, 2-hydroxy-2′-mercapto-1,1′-binaphthyl undergoes S-alkylation with BuBr and α,ω-dihalides to afford thioether species. The precursor to MTB, 2-(N,N-dimethylcarbamoyloxy)-2′-(N,N-dimethylcarbamoylthio)-1,1′-binaphthyl, undergoes anionic Fries rearrangement of the O-aryl carbamate to afford a crystallographically characterised amido species. Hydrolysis of this species affords the 3-C(O)NMe2 analogue of MTB. These MTB-based ligand systems have been tested in asymmetric conjugate addition reactions of cyclic and acyclic enones and compared with 1,1′-bi(2-thionaphthol). Active catalysts are formed in all cases but only low enantioselectivities are realised (0–55% ee). Full conditions for the separation of the enantiomeric conjugate addition products are reported.

ChemInform Abstract: [1,2]‐Anionic Rearrangement of 2‐Benzyloxypyridine and Related Pyridyl Ethers.

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.

Gas‐phase intramolecular anion rearrangements of some trimethylsilyl‐containing systems revisited. A theoretical approach

Ab initio calculations at the CCSD(T)/6-311++G(2d,p)//B3LYP/6-311++G(d,p) level of theory have been carried out for three prototypical rearrangement processes of organosilicon anion systems. The first two are reactions of enolate ions which involve oxygen-silicon bond formation via three- and four-membered states, respectively. The overall reactions are: CH(2) = C(O(-))Si(CH(3))(3) --> (CH(3))(3)SiO(-) + CH(2)C, and (CH(3))(3)SiCH = CHO(-) --> (CH(3))(3)SiO(-) + C(2)H(2). The DeltaG (reaction) values for the two processes are +175 and +51 kJ mol(-1), with maximum barriers (to the highest transition state) of +55 and +159 kJ mol(-1), respectively. The third studied process is the following: (CH(3)O)C(=CH(2))Si(CH(3))(2)CH(2)(-) --> (CH(3))(2)(C(2)H(5))Si(-) + CH(2)CO, a process involving an S(N)i reaction between -CH(2)(-) and CH(3)O- followed by silicon-carbon bond cleavage. The reaction is favourable [DeltaG(reaction) = -39 kJ mol(-1)] with the barrier for the S(N)i process being 175 kJ mol(-1). The previous experimental and the current theoretical data are complementary and in agreement.

1,2]-Anionic Rearrangement of 2-Benzyloxypyridine and Related Pyridyl Ethers

An anionic rearrangement of 2-benzyloxypyridine is described. Pyridine-directed metalation of the benzylic carbon leads to 1,2-migration of pyridine via a postulated associative mechanism (addition/elimination). Several aryl pyridyl carbinols were obtained in high yields. A formal synthesis of carbinoxamine, an antihistamine drug used for the treatment of seasonal allergies and hay fever, emerges from this methodology.

Thermodynamically Favored Anion Rearrangements in Li and Na Complexes of (S)-N-α-(Methylbenzyl)allylamine

Metalation of the chiral amine (S)-N-α-(methylbenzyl)allylamine with nBuM (M = Li, Na) leads to the formation of complexes with three distinct isomeric anion forms: allylamide [(PhC(H)CH3NCH2CH═CH2)]−, 1-aza-allyl [(PhC(H)CH3NC(H)CHCH3)]−, and aza-enolate [(PhC(═CH2)N(CH2CH2CH3)]−. The anionic form is dependent on the metal, the Lewis donor, and the thermal history of the complex. From their use in asymmetric syntheses and a previously described hmpa (hexamethylphosphoramide) complex, the allylamide form predominates with Li at room temperature in the presence of monodentate donors. The use of the bidentate donor tmeda (N,N,N′,N′-tetramethylethylenediamine) results in the crystallization and characterization of the 1-aza-allylic complex (S)-{[(PhC(H)CH3NC(H)CHCH3)Li}2·tmeda]∞, in which the allylamide moiety has undergone a 1,3-sigmatropic rearrangement. In the crystal structure, the tmeda molecules bridge rather than chelate the Li cations. The tridentate donor pmdta (N,N,N′,N′,N′′-pentamethyldiethylenetr...

Electrochemically induced transformation of 4-halomethyl-4-methylcyclohexa-2,5-dien-1-ones into 3,4-dimethylphenol

Electrochemical behavior of 4-halomethyl-4-methylcyclohexa-2,5-dien-1-ones and 2,6-dibromo-4,4-dimethylcyclohexa-2,5-dien-1-one was studied. Reductive dehalogenation of cyclohexa-2,5-dien-1-ones having a halogen atom at the neopentyl-like carbon atom gives the corresponding carbanion which undergoes anionic cyclopropyl-allyl rearrangement with subsequent addition of proton to form 3,4-dimethylphenol.

Anionic N-Fries Rearrangement Induced by I-Mg Exchange

Anionic N-Fries Rearrangement Induced by I-Mg Exchange

Reaction of (1,3-dioxo-2,3-dihydro-1 H-inden-2-ylidene)propanedinitrile with N-arylisoindolines

In a multistep reaction, 3,3′-(2-aryl-2 H-isoindol-1,3-ylene)-di-(1,4-naphthoquinone-2-carbonitriles) 13a– f have been formed in 25–61% yield from a series of N-arylisoindolines 8a– f with (1,3-dioxo-2,3-dihydro-1 H-inden-2-ylidene)propanedinitrile ( 1) in aerated pyridine. The structure of one of these products ( 13f) has been unambiguously confirmed by a single crystal X-ray structure analysis. Under otherwise the same conditions, 2-(3-methoxyphenyl)-isoindoline ( 8g) and 1 gave 38% of [4-(2,3-dihydro-1 H-isoindol-2-yl)-2-methoxyphenyl]-1,3-dioxoindan-2-ylidene)acetonitrile ( 15). Rationales for these conversions involving the known rearrangement of the radical anion of 1 into the radical anion of 1,4-naphthoquinone-2,3-dicarbonitrile ( 3) are presented.

The Loss of Carbon Dioxide from Activated Perbenzoate Anions in the Gas Phase: Unimolecular Rearrangement via Epoxidation of the Benzene Ring

The unimolecular reactivities of a range of perbenzoate anions (X-C6H5CO3-), including the perbenzoate anion itself (X = H), nitroperbenzoates (X = para-, meta-, ortho-NO2), and methoxyperbenzoates (X = para-, meta-OCH3) were investigated in the gas phase by electrospray ionization tandem mass spectrometry. The collision-induced dissociation mass spectra of these compounds reveal product ions consistent with a major loss of carbon dioxide requiring unimolecular rearrangement of the perbenzoate anion prior to fragmentation. Isotopic labeling of the perbenzoate anion supports rearrangement via an initial nucleophilic aromatic substitution at the ortho carbon of the benzene ring, while data from substituted perbenzoates indicate that nucleophilic attack at the ipso carbon can be induced in the presence of electron-withdrawing moieties at the ortho and para positions. Electronic structure calculations carried out at the B3LYP/6-311++G(d,p) level of theory reveal two competing reaction pathways for decarboxylation of perbenzoate anions via initial nucleophilic substitution at the ortho and ipso positions, respectively. Somewhat surprisingly, however, the computational data indicate that the reaction proceeds in both instances via epoxidation of the benzene ring with decarboxylation resulting--at least initially--in the formation of oxepin or benzene oxide anions rather than the energetically favored phenoxide anion. As such, this novel rearrangement of perbenzoate anions provides an intriguing new pathway for epoxidation of the usually inert benzene ring.

Selective Opening of Ring C in the Morphine Skeleton by an Unexpected Cleavage of the C5−C6 Bond in Cycloadducts of Thebaine and Acyl Nitroso Compounds

[reaction: see text] Acyl nitroso cycloadducts of the alkaloid thebaine undergo an unexpected cleavage of the C5-C6 bond when treated with 2 equiv of samarium(II) iodide in THF to give novel hexahydrobenzazocine products. A proposed mechanism for the transformation involves rearrangement of the initial radical anion.

Diphosphacarbollide Analogues of the C5H5-Anion: Isolation of thenido-Di- and Triphosphacarboranes 7,8,9-P2CB8H10, [7,8,9-P2CB8H9]-, [7,8,10-P2CB8H9]-, and 7,8,9,10-P3CB7H8

Treatment of a solution of excess PCl(3) and PS (PS = "proton sponge" = 1,8-dimethylamino naphthalene) with arachno-4-CB(8)H(14) (1) in CH(2)Cl(2), followed by hydrolysis of the reaction mixture, resulted in the isolation of the eleven-vertex diphosphacarbaborane nido-7,8,9-P(2)CB(8)H(10) (2) (yield 34%) as the main product. Other products isolated from this reaction were the phosphacarboranes nido-7,8,9,10-P(3)CB(7)H(8) (3) (yield 5%) and closo-2,1-PCB(8)H(9) (4) (yield 15%). Compound 2 can be deprotonated by PS in CH(2)Cl(2) or NaH in diethyl ether to give the [nido-7,8,9-P(2)CB(8)H(9)](-) (2(-)()) anion, which gives back the original compound, 2, upon re-protonation. Thermal rearrangement of anion 2(-) (Na(+) salt) at 350 degrees C for 2 h produced the isomeric [nido-7,8,10-P(2)CB(8)H(9)](-) (5(-)()) anion, which was isolated as a PPh(4)(+) salt (yield 86%). Multinuclear ((1)H, (11)B, (31)P, and (13)C), two-dimensional [(11)B-(11)B] COSY, (1)H{(11)B(selective)}, (1)H{(31)P(selective)}, and gradient-enhanced ([(1)H-(13)C] HSQC) magnetic resonance measurements led to complete assignments of all resonances which are in excellent agreement with the structures proposed. Coupling constants, (1)J((31)P,(13)C), (2)J((31)P,C,(1)H), and (1)J((31)P,(31)P), were calculated using the DFT method B3LYP/6-311+G(d,p). The molecular geometries of all compounds were optimized ab initio at a correlated level of theory (RMP2(fc)) using the 6-31G basis set, and their correctness was assessed by comparison of the experimental (11)B and (13)C chemical shifts with those calculated by the GIAO-SCF/II//RMP2(fc)/6-31G method. The computations also include the structures and chemical shieldings of the still unknown isomers [nido-7,10,8-P(2)CB(8)H(9)](-) (6(-)) and [nido-7,9,8-P(2)CB(8)H(9)](-) (7(-)).

Cyclopropylcarbinyl → Homoallyl-Type Ring Opening of Ketyl Radical Anions. Structure/Reactivity Relationships and the Contribution of Solvent/Counterion Reorganization to the Intrinsic Barrier

[reaction: see text] Following a protocol developed by Mathivanan, Johnston, and Wayner (J. Phys. Chem. 1995, 99, 8190-8195), the radical anions of several cyclopropyl- and oxiranyl-containing carbonyl compounds were generated in an effort to measure the rate constants for their ring opening (k(o)) by laser flash photolysis. The results of these experiments are compared to those obtained from earlier electrochemical studies, and the combined data set is used to rationalize the kinetics of radical anion ring opening in a general context by using Saveant's theory pertaining to stepwise dissociative electron transfer (Acc. Chem. Res. 1993, 26, 455-461). Compared to cyclopropylcarbinyl --> homoallyl rearrangements of neutral free radicals, at comparable driving force, the radical anion ring openings are slightly slower. The small difference in rate is attributed to the contribution of an additional, approximately 2 kcal/mol, solvent reorganization component for the radical anion rearrangements. The solvent reorganization energy for ring opening of these radical anions is believed to be small because the negative charge does not move appreciably in the progression reactant --> transition state --> product.

Synthesis of Enantiopure tert‐Butanesulfinamide from tert‐Butanesulfinyloxazolidinone.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Hormaomycin Analogues by Precursor‐Directed Biosynthesis – Synthesis of and Feeding Experiments with Amino Acids Related to the Unique 3‐(trans‐2‐Nitrocyclopropyl)alanine Constituent

AbstractThe deuterium‐labeled racemic 3‐(trans‐2‐nitrocyclopropyl)‐alanine (rac‐[D2]‐3) and 3‐(trans‐2‐aminocyclopropyl)alanine (rac‐[D2]‐4) as well as non‐labeled rac‐3‐[trans‐2‐(hydroxycarbonyl)cyclopropyl]alanine (rac‐5a) and rac‐3‐[trans‐2‐(methoxycarbonyl)cyclopropyl]alanine (rac‐5b) were prepared in 43, 18, 88 and 49 % overall yield, respectively, along a general synthetic route applying alkylations of the lithium enolate of tert‐butyl (diphenylmethylene)‐aminoacetate (O’Donnel’s glycine equivalent 11) as a key step. Feeding experiments with these amino acids and Streptomyces griseoflavus (strain W 384) revealed that rac‐[D2]‐3, rac‐5a and rac‐5b are incorporated to give hormaomycin 1b and its analogue 23, respectively, while rac‐[D2]‐4 is not. Feeding of rac‐2‐(trans‐2‐nitrocyclopropyl)glycine (rac‐6) unexpectedly gave the 5‐nitronorvaline‐containing hormaomycin analogues 25a–c. This is rationalized as arising from a cyclopropyl to homoallyl anion rearrangement followed by enzymatic hydrogenation of the double bond. These experiments provided new insights into the substrate specificity of the enzyme which assembles hormaomycin. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Harnessing Anionic Rearrangements on the Benzenoid Ring of Quinoline for the Synthesis of 6,6‘-Disubstituted 7,7‘-Dihydroxy-8,8‘-biquinolyls

7,7'-Bis(((dimethylamino)carbonyl)oxy)-8,8'-biquinolyl (5) was prepared in 71% yield by regioselective directed ortho metalation (DoM) of N,N-dimethyl O-quinol-7-yl carbamate (2) with LDA followed by oxidation with anhydrous ferric chloride. DoM of 5 with excess LDA induced double anionic ortho-Fries rearrangement and gave 6,6'-bis((dimethylamino)carbonyl)-7,7'-dihydroxy-8,8'-biquinolyl (8). Treatment of N,N-diethyl O-(8-iodoquinol-7-yl) carbamate (16) with LDA in THF solvent at -78 degrees C, followed by addition of anhydrous ferric chloride, resulted in an efficient tandem halogen-dance dimerization process which afforded 7,7'-bis(((diethylamino)carbonyl)oxy)-6,6'-diiodo-8,8'-biquinolyl (17) directly in 54% yield.