1,2-dihydroisoquinolines—XVIII Rearrangements—IV Dihydroisoquinoline rearrangement—15

When 1-allyl-2-methyl-1,2-dihydropapaverine is treated with hot, dilute mineral acid, rearrangement occurs to give, almost exclusively the 3-allyl-2-methyl-3,4-dihydropapaverinium salt. The previously reported rearrangement of 1-cinnamyl-2-methyl-6,7-dimethoxy-1,2-dihydroisoquinoline has been re-examined and the earlier result, that rearrangement occurs yield the 3-cinnamyl-3,4-dihydroisoquinolinium salt, confirmed.     

Reverse aromatic cope rearrangement of 2-allyl-3-alkylideneindolines driven by olefination of 2-allylindolin-3-ones: synthesis of alpha-allyl-3-indole acetate derivatives

The reverse aromatic Cope rearrangement of 2-allyl-3-alkylideneindolines obtained by Horner-Wadsworth-Emmons olefination of 2-allylindolin-3-ones was performed. When 2-allylindolin-3-ones were treated with phosphonium ylides in refluxing toluene, domino Wittig reaction and reverse aromatic Cope rearrangement took place to give alpha-allyl-3-indole acetate derivatives in good yields. The aromatization as a new driving force in the Cope rearrangement is preferable to the conjugation with the carbonyl and cyano groups and also to the alkyl substitution pattern, which are well-known driving forces.     

Molecular rearrangements—II: The pyrolysis of benzyl-β-naphthyl ether

When purified benzyl-β-naphthyl ether was heated at 260°, in absence of any promotor, the benzyl group migrated to the α-position of the naphthol nucleus. β-Naphthol, toluene, dibenzyl and 9-phenyl-1,2,7,8-dibenzoxanthene also were formed. When quinoline was used as a solvent, the normal rearrangement products were obtained together with 2- and 4-benzylquinolines and 1(2-quinolyl)2-naphthol and its isomeric 1(4-quinolyl)2-naphthol. When phenol and anisole were used as solvents, the rearrangement was accompanied with benzylation of the solvent.     

Phosphates D'énols: XI—Étude en Spectrométrie de Masse des Dérivés Diméthyliques

The mass spectrometric study of a series of enolic phosphates of type A leades to fragmentation patterns influenced by the nature of the substituents (R, R′ and R″). It is generally observed that a simple or double hydrogen rearrangement occurs with the loss of the enolic groups. When R and R′ are alkyl groups, the migrating groups are the hydrogen atoms on the alkyl group at position 1. When there is no alkyl group at position 1, the hydrogen atoms of the alkyl group at position 2 induce the rearrangement process. Finally, if R, R′ and R″ are hydrogen atoms, the loss of the enolic chain occurs without any rearrangement.     

Combined C-H activation/cope rearrangement as a strategic reaction in organic synthesis: total synthesis of (-)-colombiasin a and (-)-elisapterosin B

The total synthesis of (-)-colombiasin A (2) and (-)-elisapterosin B (3) has been achieved. The key step is a C-H functionalization process, the combined C-H activation/Cope rearrangement, between methyl (E)-2-diazo-3-pentenoate and 1-methyl-1,2-dihydronaphthalenes. When the reaction is catalyzed by dirhodium tetrakis((R)-(N-dodecylbenzenesulfonyl)prolinate), Rh(2)(R-DOSP)(4), an enantiomer differentiation step occurs where one enantiomer of the dihydronaphthalene undergoes the combined C-H activation/Cope rearrangement while the other undergoes cyclopropanation. This sequence controls the three key stereocenters in the natural products such that the remainder of the synthesis is feasible using standard chemistry.     

单重态H_2N=B:→HNBH重排反应的理论研究

用量子化学中的从头算方法, 在MP2/6-311++G(d,p)水平上研究了单重态H_2N=B→HNBH重排反应的机理。结果表明, 该重排反应经过一个三元环过渡态。根据计算结果，初步讨论了该反应的热力学及动力学函数。     

A New Zincate‐Mediated Rearrangement Reaction of 2‐(1‐Hydroxyalkyl)‐1‐alkylcyclopropanol

A novel rearrangement of 2‐(1‐hydroxyalkyl)‐1‐alkylcyclopropanol has been found. It proceeds in the presence of a catalytic amount of organozinc ate complex to give vic‐diols. The rearrangement can be applied to various types of 2‐(1‐hydroxyalkyl)‐1‐alkylcyclopropanol, which can be easily prepared from the corresponding α,β‐epoxyketones and bis(iodozincio)methane. When bicyclo[13.1.0]pentadecane‐1,15‐diol was treated with the organozinc ate complex, the corresponding 14‐membered cyclic vic‐diol was obtained. Thus, this rearrangement is also useful for changing the ring size of cyclic substrates.     

The mechanism of the chapman rearrangement of N-arylbenzimidate on the basis of the molecular structure established by X-ray. Part II

Dibenz[c,h]acridine ( 13 ) was formed directly by the Chapman rearrangement of 2-methoxycarbonyl-1-naphthyl-N-1′-naphthylbenzimidate ( 11 ) without isolation of intermediate 12 . When the Chapman rearrangement was carried out under mild reaction conditions, the intermediate 12 was isolated in high yield, whose structure was determined by the X-ray studies. The mechanism of the Chapman rearrangement can be interpreted on the basis of the X-ray data of 11 and 12 .     

Novel rearrangement of an isocaryolane sesquiterpenoid under mitsunobu conditions

Under modified Mitsunobu reaction conditions, a novel skeleton rearrangement of terpenes has been obtained. The reactivity of 8, 9-dioxygenated isocaryolane derivatives has been investigated. When either (8R,9R)-8-methoxyisocaryolane-9-ol (7) or (8R, 9R)-isocaryolane-8,9-diol (10) are treated under acidic conditions, isocaryolan-9-one (9) and the rearrangement compound (1S,2S,5R,8S)-1, 4,4-trimethyltricyclo[6.2.1.0(2,5)]undecane-8-carbaldehyde (11) are obtained. Otherwise treatment of compounds 7 and 10 under modified Mitsunobu conditions leads to the novel sesquiterpene derivative (1S, 2S,5R,9R)-1,4,4-trimethyltricyclo[7.2.1.0(2,5)]dodecan-8-one (8). This is the first example, to our knowledge, of a Mitsunobu-induced pinacol rearrangement. The influences of the substrate and reaction conditions on the evolution of the reaction are both explored. This modification of the Mitsunobu reaction conditions introduces a new, one-pot, procedure for preparing this class of rearrangement product.     

Novel rearranged ions observed for

C-terminal rearrangement ions [b(n-1) + H2O] (where n refers to the total number of residues of peptides) are frequently observed for peptides which contain basic amino acid(s), especially arginine, at or near their N termini in low- and high-energy collision-induced dissociation or post-source decay (PSD) spectra. Here we report a novel rearrangement, associated with PSD for serine- or threonine-containing peptides that are susceptible to C-terminal rearrangement. Based on PSD analyses of serine- or threonine-containing bradykinin and its analogs, which have been ethyl-esterified or 18O labeled at their C termini, the [b(k) + H2O] (where k denotes the position adjacent to the left of the Ser/Thr residue) ion is generally thought to be formed by the transfer of the hydroxyl moiety of a serine or threonine residue to the carbonyl group of the residue to its left accompanied by the loss of the remaining C-terminal portion of the peptide. When the Ser/Thr is at or near the C terminus, the present [b(k) + H2O] ion could be formed via two pathways, i.e., the Ser/Thr-related rearrangement and the conventional C-terminal rearrangement, which has been clearly verified by 18O labeling at the C terminus. In addition, the ions which are formally designated as [y(m)b(l) + H2O], where y(m)b(l) denotes a b-type internal ion, are also briefly described.     

A novel rearrangement of 2(5H)-furanones

A novel rearrangement of 2(5H)-furanones is described. When refluxed in aq. Ethanolic solution in the presence of excess KOH, the 2,5-dihydro-2-oxofuran-3-carboxamides 6 underwent a novel rearrangement to the corresponding 4,5-dihydro-4-oxo-2-(phenylamino)-3-furancarboxylic acids 1 in moderate-to-excellent yields.     

A New Synthesis of 3-Chloro Butenolides via Rearrangement of 3,3-Dichloro Beta Lactones

4,4-Dialkyl 3,3-dichloro oxetan-2-ones rearrange under Lewis acid catalysis, accompanied by loss of HC1, to afford 4,5-dialkyl 3-chloro butenolides.

We have recently been investigating the reactions of beta lactones under the influence of Lewis acid catalysis.¹ When the lactone ring oxygen is bonded to a secondary carbon atom, a rearrangement occurs in which the beta lactone 1 expands to a butyrolactone 4 with the concommitant migration of a hydrogen or carbon atom into the lactone ring.² If the oxygen is bonded to a tertiary carbon, an ionization/elimination sequence ensues, producing a β, γ-unsaturated carboxylic acid     

Regioselective synthesis of 2,3,4- or 2,3,5-trisubstituted pyrroles via [3,3] or [1,3] rearrangements of O-vinyl oximes

The regioselective synthesis of 2,3,4- or 2,3,5-trisubstituted pyrroles has been achieved via [3,3] and [1,3] sigmatropic rearrangements of O-vinyl oximes, respectively. Iridium-catalyzed isomerization of easily prepared O-allyl oximes enables rapid access to O-vinyl oximes. The regioselectivity of pyrrole formation can be controlled by either the identity of the α-substituent or through the addition of an amine base. When enolization is favored, a [3,3] rearrangement followed by a Paal-Knorr cyclization provides a 2,3,4-trisubstituted pyrrole; when enolization is disfavored, a [1,3] rearrangement occurs prior to enolization to produce a 2,3,5-trisubstituted pyrrole after cyclization. Optimization and scope of the O-allyl oxime isomerization and subsequent pyrrole formation are discussed and mechanistic pathways are proposed. Conditions are provided for selecting either the [3,3] rearrangement or the [1,3] rearrangement product with β-ester O-allyl oxime substrates.     

二价钌催化的金属卡宾经由的硫叶立德[2,3]-σ重排反应研究

报道烯(炔)基硫醚与α-重氮羰基化合物, 在[RuCl₂(p-cymene)]₂催化下, 经由金属卡宾发生硫叶立德[2,3]-σ重排反应(Doyle-Kirmse反应). 在Ru(II)作用下, α-重氮羰基化合物与烯丙基硫醚的反应以较好收率生成相应的[2,3]-σ重排产物高烯丙基硫醚. 同样条件下与炔丙基硫醚的反应则生成[2,3]-σ重排产物联烯和呋喃衍生物, 后者是联烯进一步在Ru(II)作用下重排的产物.     

Synthesis of protected gamma-carboxyglutamates and gamma-acylglutamates by rearrangement of N,N-diacylglutamates

A new method for gamma-acylation of protected glutamic acids, involving intramolecular rearrangement of an acyl urethane, has been devised to prepare the protected gamma-carboxyglutamates 7, 9 and 11 and the protected 4-acylglutamates 15 and 22 from N,N-bisurethanes or N-acyl-N-urethanes of general structure 1. When the formyl-urethane 17 was used in the reaction, then the intermediate 18 in the intramolecular rearrangement was obtained.     

Thio-claisen rearrangements of some ketene derivatives

A number of 1-allylthio and 1-crotylthio 1-aminoalkenes derived from ketones and active methylene compounds has been prepared and rearranged to the corresponding thioamides (thio-Claisen rearrangement). Besides rearrangement products, small amounts of 1-alkyl-thio-N-alkyl-N-phenyl-1-aminoalkenes have also been isolated. When the ketene derivatives did possess a H-atom on nitrogen, cleavage of the formed thioamide produced phenyl isothiocyanate and substituted active methylene compounds.     

Dehydration Rearrangements of Derivatives of Methylenedihydrobenzofuran - a New Path to Substituted Benzofurans

When heated with acidic agents derivatives of 3-amino-2-(hydroxydialkylmethyl)methylene-2,3-dihydrobenzofuran undergo rapid dehydration and rearrangement to substituted 2-alkenyl-3-aminobenzofurans.     

Imide-amide rearrangement of oxazaphosphorimidates: studies towards the application to the synthesis of chiral Lewis bases

The Lewis acid catalysed imide-amide rearrangement of oxazaphosphorimides to diazaphoshoramides is reported for the first time. In spite of the similarity to the previously reported Lewis acid catalysed imide-amide rearrangement of dioxaphosphorimides to oxazaphosphoramides we show that this rearrangement proceeds by a different mechanism, not involving the formation of an oligomeric intermediate. The oxazaphosphorimides are prepared in situ by the Staudinger reaction of the appropriate trivalent phosphorus compound with an azide and after the addition of BF₃·OEt₂, undergo rearrangement to the corresponding diazaphosphoramides. We have found that the rearrangement occurs with retention of configuration at the phosphorus atom and inversion of configuration at the rearranged carbon atom. When starting from chiral 1,2-aminoalcohol, substituted at the carbon atom that undergoes rearrangement, a mixture of diastereomers is obtained, but the diastereomeric ratio, initially obtained in the formation of the trivalent phosphorus compounds is maintained during the whole transformation. This implies that if the rearrangement is to be used for the preparation of chiral phosphoramides with defined stereochemistry at the phosphorus atom, a high diastereoselectivity during the preparation of the trivalent phosphorus precursors should be obtained.     

Anhydrodihydroartemisinin and its 10-trifluoromethyl analogue: access to novel d-ring-contracted artemisinin trifluoromethyl ketones

The preparation of the 10-trifluoromethyl hydroartemisinin, followed by dehydration, afforded the trifluoromethyl analogue 2 of anhydrodihydroartemisinin 1. The reactivity of these two glycals of artemisinin were compared in epoxidation and halogenation reactions. Iodination of glycal 1 in water and the further rearrangement of the produced iodo hemiacetal provided the new D-ring-contracted aldehyde 8alpha, where the methyl at C-9 is beta. Epoxidation of 10-trifluoromethyl anhydrodihydroartemisinin 2 stereoselectively provided the beta-epoxy ether 11 in high yield. When treated with hexafluoro-2-propanol or trifluoroethanol, 11 readily underwent a rearrangement yielding to the D-ring-contracted trifluoromethyl ketone 9alpha with retention of configuration at C-9.     

Furan ring opening–indole ring closure: recyclization of 2-(2-aminophenyl)furans into 2-(2-oxoalkyl)indoles

The acid-catalyzed rearrangement of 5-alkyl-2-[2-(sulfonylamino)phenyl]furans into 2-(2-oxoalkyl)indoles is described. When the N-sulfonyl group in the starting compounds was displaced by an N-acyl group, the corresponding indoles were not formed under the same reaction conditions due to the in situ indole deacylation and decomposition. The presence of an alkyl group at the C5 position of the furan ring is also crucial for the efficiency of the process. The discussed rearrangement provides a simple and efficient approach to 2-(2-oxoalkyl)indoles.