Showing papers on "Carroll rearrangement published in 1973"

Geltungsbereich und Mechamismus der durch Silberionen katalysierten Propargylester‐Allenylester‐Umlagerung nach Saucy und Marbet

Abstract: The mechanism of the catalysis of the reversible (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) by silver(I) ions was investigated, using optically active and diastereoisomeric esters as well as 14C- and 18O-labelling. In order to work with crystalline materials, mainly p-nitrobenzoates (10, 11: R4 = pO2NC6H4) were used. In some cases the rearrangement 10 ⇄ 11 was studied using acetates (R4 = CH3). The alkyl substituents R1, R2, R3, were widely varied (cf. Tables 1, 2). The solvents in which the rearrangements were performed were in most cases dry chlorobenzene and 96% aqueous dioxane. Silver tetrafluoroborate, the benzene complex of the latter, and silver trifluoroacetate (in chlorobenzene) as well as silver nitrate (in aqueous dioxane) served as catalysts. The amounts of the silver catalysts used varied between 0,5 and 10 mol-%; reaction temperatures applied were in the range 35–95°, The results obtained are as follows: 1 The rate-determining step of the (propargyl ester)/(allenyl ester) rearrangement (10 ⇄ 11) occurs in a silver(I) complex with the substrates (10, 11), which is formed in a pre-equilibrium. This follows from kinetic experiments (cf. Fig. 6, 7, 8, 10) and the fact that the rate of rearrangement (of 10a) is strongly decreased when cyclohexene is added (cf. Fig. 9). In solvents which are known to form complexes with silver(I) ions the rate of rearrangement (of 10a)is much slower than in solvents with similar dielectric constants but with small capacity for complex formation with silver(I) ions (cf. Table 4). Taking into account what is known about silver(I)-alkene and -alkyne complexes (cf. [18]), it is obvious that the (propargyl ester)/(allenyl ester) rearrangement occurs in a π-complex of the silver(I) ion with the triple bond in the propargyl ester or one of the two C,C double bonds in the allenyl ester, respectively. 2 The shift of the carboxyl moiety in the reversible rearrangement 10 ⇄ 11 occurs intramolecularly. p-Nitrobenzoic acid-[carboxyl-14C] is not incorporated during the rearrangement, neither in the reactant 10 nor in the product 11 and vice versa. A crossing experiment gave no mixed products (cf. Scheme 2, p. 882). 3 An internal ion pair can be excluded for the rearrangement 10 ⇄ 11 because the 18O-carbonyl label in the reactant is found exclusively in the alkoxy part of the product (cf. Scheme 3, p. 886, and Table 9). Thus, the rearrangement 10 ⇄ 11 occurs with inversion of the carboxyl moiety. 4 The rearrangement of optically active propargyl esters (10g, 10i) leads to completely racemic allenyl esters (11g, 11i). However, rearrangement of erythro- and threo-10j-[carbonyl-18O] (Scheme 3) shows that the stereospecifically formed allenyl esters erythro- and threo-11j-[18O]-epimerize rapidly in the presence of silver(I) ions. This epimerization is twice and forty times, respectively, as fast as the rearrangement of the corresponding propargyl esters (cf. Fig. 1–5). During epimerization or racemization the 18O-label is not randomized (cf. also Scheme 4, p. 898). 5 The equilibrium of the rearrangement 10 ⇄ 11 depends on the bulkiness of the substituents R1, R2, R3 and of the carboxyl moiety (cf. Table 2). Taking into account these facts (points 1–5), the reversible (propargyl ester)/(allenyl ester) rearrangement promoted by silver(I) ions can be described as a [3s, 3s]-sigmatropic reaction occurring in a silver(I)-π-complex with the C,C triple bond in 10 and a C,C double bond in 11. It is suggested that complex formation in 10 and 11 occurs with the π-bond which is not involved in the quasicyclic (containing six orbitals and six electrons) transition state of the rearrangement (Fig. 11). Thus, the rearrangement is of a type which has recently been called a charge-induced sigmatropic reaction (cf. [26]). Therefore, in our case, the catalysis by silver(I) ions is of a different type from that of transformations of strained cyclic molecules promoted by silver(I) ions (cf. [14] [16] [27]–[31]). Side reactions. Whereas the rearrangement of propargyl esters 10 in presence of silver tetra- fluoroborate in chlorobenzene or silver nitrate in aqueous dioxane leads to the corresponding allenyl esters 11, the rearrangement of 10 with silver trifluoroacetate, especially in the presence of trifluoroacetic acid, results in the formation of the dienol esters 12 and 13, which clearly are derived from 11 (see Scheme 1, p. 881). As shown by the rearrangement of 11 in the presence of p-nitrobenzoic acid-[carboxyl-14C], 12 and 13 arise in part from a not isolated di-p-nitrobenzoate (cf. Scheme 6, p. 905), since radioactivity is found in 12 and 13.

Catalytic Rearrangement of Xanthates to Dithiolcarbonates

Abstract: During a research of the Friedel-Crafts'reaction using xanthate, it was found thatxanthates rearrange to dithiolcarbonates by the catalysis of aluminum chloride in carbondisulfide. This rearrangement needs at least a molar equivalent of aluminum chlorideto xanthates and proceeds even at room temperature. With respect to solvent, carbon disulfide can be replaced by chloroform without essential effect on the product distribution. It was presumed from a study of crossover reaction that this rearrangement might have the nature of intermolecular reaction.

Sequential Claisen and Cope rearrangements: the propenyl ether and acetate of 3-methylhept-6-en-1-yn-3-ol

Abstract: The synthetic potential of a Claisen followed by a Cope rearrangement is illustrated by the reactions of 3-methylhept-6-en-1-yn-3-ol (II). This propargylic alcohol (II) condenses with methyl isopropenyl ether with Claisen rearrangement to give 6-methyldeca-4,5,9-trien-2-one (IV), which isomerises in boiling xylene through the product of Cope rearrangement (V) to 5-isopropylideneocta-trans-3,7-dien-2-one (VI). The acetate (IX) of the alcohol (II) undergoes an analogous series of rearrangements to the allenyl acetate (X) and the dienyl acetate (XII).

The mechanism of the rearrangement of β-acyloxyalkyl radicals

Abstract: Determination of the distribution of products from decarbonylation of 2-formyl-1,1-dimethylethyl heptanoate (6d) and other esters of 3-hydroxy-3-methylbutanal, and from the reaction of tributylstannane with 2-bromo-1,1-dimethylethyl benzoate (11b), 2-bromo-1-methyl-1-phenylethyl acetate (11c), and similar bromo-esters, has enabled the rates of rearrangement of some β-acyloxyalkyl radicals to be evaluated. The kinetic data together with the results of reactions using 18O labelled substrates indicate that 1,2-acyloxy-transfer proceeds via a concerted mechanism involving a five-membered cyclic transition state. The rate of rearrangement of the 2-acetoxy-2-phenylpropyl radical (12c) by 1,2-aryl migration has also been determined.

Unsaturated carbohydrates. Part XVII. Synthesis of branched-chain sugar derivatives by application of the Claisen rearrangement

Abstract: 2,3-Dideoxy-4-O-vinylhex-2-enopyranoside derivatives on heating to 180° undergo the Claisen rearrangement to give 2,3,4-trideoxy-2-C-(formylmethyl)hex-3-enopyranoside isomers. Suprafacial [3,3] sigmatropic processes are involved, so that stereochemical integrity is maintained at the allylic centres. The reaction represents a novel means whereby branch points can be introduced into carbohydrates.

Base-promoted rearrangement of 2,3,5,6-tetrachloropentacyclo-[5.4.0.02,6.03,10.05,9]undecane-4,8,11-trione

Abstract: Reaction of the title compound (III) with an excess of sodium hydroxide in refluxing toluene results in a novel rearrangement, affording 6-chloro-cis-1,2-dihydrobenzocyclobutene-1,2,3-tricarboxylic acid (IVa).

Synthesis of unsaturated aldehydes by sequential Claisen and Cope rearrangements

Abstract: Condensation of hexa-1,5-dien-3-ol (Ia) with 1,1,3-triethoxy-2-methylbutane, catalysed by o-nitrobenzoic acid, proceeds with elimination of three moles of ethanol to form an intermediate dienol ether that undergoes Claisen rearrangement to 2-methyl-2-vinylocta-4,7-dienal (Va). At higher temperatures (ca. 160°) this aldehyde (Va) rearranges to 2-methyl-5-vinylocta-2,7-dienal (VIa), which at still higher temperatures (ca. 190°) equilibrates through a second Cope rearrangement with the more stable 2-methyldeca-2,5,9-trienal (VIIa). The same sequence of reactions was carried through with two methyl derivatives of the hexadienol (Ia).Reduction of the aldehyde (VIa) formed the allyl alcohol (X), which rearranged to the same dimethylated straight-chain alcohol (XI) as was produced by reduction of the isomer (VIIa). Condensation with 1,1,3-triethoxy-2-methylbutane converted (X) through Claisen rearrangement and two successive Cope rearrangements into the ‘linear’ 2,6-dimethyltetradeca-2,6,9,13-tetraenal (XV), also formed in the same way from the rearranged isomer (XI) through Claisen rearrangement and one Cope rearrangement.

ortho Diquaternary Aromatic Compounds. IV. Acid-catalyzed Rearrangements of Polyalkyltetralones and Related Ketones

Abstract: The ketones 1,1,4,4-tetramethyl-2-tetralone (1a), 1,1,4,4,7-pentamethyl-2-tetralone (1b), and 1,1,4,4,6-pentamethyl-2-tetralone (1c) undergo rearrangement on heating with aluminum chloride or ferric chloride in tetrachloroethane or nitromethane into mixtures of their respective isomeric ketones, 1-acetyl-1,3,3-trimethylindane (2a) and 2,2,4,4-tetramethyl-1-tetralone (3a) from 1a, 1-acetyl-1,3,3,6-tetramethylindane (2b) and 2,2,4,4,7-pentamethyl-1-tetralone (3b) from 1b, and 1-acetyl-1,3,3,5-tetramethylindane (2c) and 2,2,4,4,6-pentamethyl-1-tetralone (3c) from 1c. A quantitative study using g.l.c. of the distribution of the ketones with time shows that the sequence of the rearrangement is: . A methyl group homologously para to the carbonyl (1c) accelerates the rearrangement. The same kind of rearrangement takes place during Friedel–Crafts cyclialkylation with 2,2,5,5-tetramethyltetrahydrofuranone. A unifying reaction mechanism is postulated to account for the rearrangements. This mechanism also accounts f...

The wittig rearrangement of (diarylmethoxy)acetamides

Abstract: N,N-Dialkyl-2-(arylmethoxy)- or N,N-dialkyl-2-(diarylmethoxy)acetamides were found to undergo a Wittig rearrangement under the influence of bases such as sodium hydride to form either N,N-dialkyl-3-aryl- or 3,3-diaryllactamides. When the diarylmethoxy group was asymmetric, the rearrangement resulted in diastereoisomeric reaction products. Ortho substitution in one or both aryl rings altered the course of rearrangement with the result that additionally, or even exclusively, p-benzylmandelic amide derivatives were formed. Not only rearrangement products but also byproducts like diaryl ketone, diarylmethane and tetraarylethane were formed. The formation of the latter compound would indicate that radicals are somehow involved in the reaction mechanism. To date, attempts to obtain more than circumstantial evidence for such a mechanism have failed. In several cases byproducts with the structure of a substituted p-benzylbenzoic acid were isolated. These acids were found to arise from the above “para rearrangement” products by further decomposition under the influence of the basic catalyst. The scope of the reaction was explored by studying the rearrangement of some thirty ethers.

The association of the Claisen rearrangement with a novel [1,5] sigmatropic rearrangement

Abstract: Thermal rearrangement of the allyl aryl ether (5) gave, in addition to the expected Claisen rearrangement product (6), the isomer (7), and similarly thermal transformation of the allyl ether (8) gave the mixture (9) and (10); the formation of (7) and (10) is rationalised as involving a [1,5] acetyl shift.

Annelated furans. XII. Fries rearrangement of isocreosol esters

Abstract: The Fries reaction of 2-methoxy-5-methylphenyl butyrate (5) in the presence of titanium tetrachloride gave only the para rearrangement product, 4-hydroxy-5-methoxy-2-methylphenyl propyl ketone (6). Irradiation of the ester (5) gave the ortho rearrangement product, 2- hydroxy-3-methoxy-6-methylphenyl propyl ketone (7), in addition to (6), isocreosol, and 2-hydroxy-4-methylphenyl propyl ketone (8). The photorearrangement of 3-nitropropionate esters of isocreosol and related phenols did not proceed satisfactorily as the 3-nitropropionyl group appeared unstable under these conditions. However, the photo- Fries rearrangement of the corresponding 3-chloropropionate esters proceeded normally with the formation of o- and p-hydroxyphenyl 2- chloroethyl ketones, and in addition the substituted o-hydroxyphenyl vinyl ketones, generated by elimination of hydrogen chloride from the corresponding ortho rearrangement product.

1.5-Dienes from allylic alcohols and carbonyl compounds by successive Claisen rearrangement, Wittig reaction, and Cope rearrangement: an attempted synthesis of ‘propylure’

Abstract: 3,3-Dialkylallyl alcohols and aldehyde dimethyl acetals condense with Claisen rearrangement to form substituted pent-4-enals. The hexa-1,5-dienes made from these aldehydes by the Wittig reaction then rearrange in the opposite direction according to Cope. While this scheme worked very well with n-heptanal dimethyl acetal and 3-methylbut-2-en-1-ol, yielding 2-methyldodeca-2,6-diene, it was less successful when applied to an attempted synthesis of ‘propylure’[(5E)-10-propyltrideca-5,9-dienyl acetate].

The Solvent Effect in the Rearrangement of 4- (N-Allyl-N-tosylamino) Naphthal-N-methylimide

Abstract: The rates of rearrangement of 4- (N-allyl-N-tosylamino) naphthal-N-methylimide (1) at 205, 215 and 225°C in 9 solvents have been determined. The rearrangement was a first order reaction in every case and so insensitive to the nature of the solvent that the rates varied within only a 3.4-fold range. Hydroxylic solvents such as ethylene glycol and phenol were relatively useful for accellerating the reaction. The entropies of activation had negative values.These results show that the rearrangement proceeds via a transition state similar to that of the usual Claisen rearrangement.