Claisen Rearrangement Products Research Articles

ChemInform Abstract: 2‐Fluoro‐ and 5‐Fluoro‐3,4‐dimethylphenethylamine Derived from Claisen Rearrangement Products.

AbstractBei der thermischen oder der durch AlCl3 katalysierten (Claisen‐Umlagerung des Allylethers (I) wird ein Gemisch aus (II) und (III) bei nachfolgender Methylierung isoliert, deren Strukturen durch Überführung in die Phenethylamine (IV) und (V) gesichert werden.

Partially fluorinated heterocyclic compounds. Part 22. The preparation of allyl 2,5,6-trifluoropyrimidin-4-yl ether and related compounds and a study of their Claisen rearrangement reactions. A new route to 5-fluorouracil and barbituric acid derivatives

Vapour phase thermolyses of allyl 2,5,6-trifluoropyrimidin-4-yl, (1), 2,5-difluoro-6-methoxypyrimidin-4-yl, (5), 2,5-difluoropyrimidin-4-yl, (6), and 5,6-difluoro-2-methoxypyrimidin-4-yl, (7), ethers gave the Claisen rearrangement products (2), (17), (18), and (20) respectively, in which N-3 is the migration terminus, but the 2-allyl derivative (10) was inert. In other thermolyses with allyl 5-fluoropyrimidin-4-yl ethers where a preliminary reaction results in the localisation of the C-4 to C-5 double bond, C-5 is the migration terminus: barbituric acid derivatives (28) and (26) are formed from (5) and allyl 2,5-difluoro- 6-hydroxypyrimidin-4-yl ether (13) respectively after hydrolysis of each rearrangement product and (14) also gave (26); 2,4-diallyl-5-fluoro-6-methoxypyrimidine (11) gave (29)(with the loss of CH3) and 2,4,6-triallyloxy-5-fluoropyrimidine (12) was isomerised to (30). Allyl 2,6-dimethoxy-5-fluoro- pyrimidin-4-yl ether (8) gave both N-3 and C-5 migration termini products (21) and (33) respectively. Hydrolysis of (2), (17), and (18) gave the 5-fluorouracil derivatives (22), (23), and (24) respectively.

2-fluoro- and 5-fluoro-3,4-dimethylphenethylamine derived from claisen rearrangement products

The Claisen rearrangement of 2-allyloxy-3-fluoroanisole followed by methylation provided the para -rearranged product along with the unexpected 3-(3,4-dimethoxy-2-fluorophenyl)-1-propene.

Aliphatic Claisen Rearrangement Promoted by Organoaluminium Reagents

Abstract Organoaluminium compounds, R3Al, promote the Claisen rearrangement of allyl vinyl ether derivatives at room temperature under transfer of R or H as a nucleophile to the aldehydic carbon. Treatment of 1-butyl-2-propenyl vinyl ether with a hexane solution of Me3Al (1.0 M, 2.2 equiv) in CH2ClCH2Cl at 25 °C afforded 5-decen-2-ol (91% yield, E⁄Z=47⁄53), which was produced by the [3,3] sigmatropic rearrangement and successive methylation. The rearrangements with alkynylation, alkenylation, and hydrogenation are also achieved. The regular Claisen rearrangement products, or γ,δ-unsaturated aldehydes (ketones), are obtained at 25 °C in good to excellent yields with Et2AlSPh (2.5 equiv) or the combination of Et2AlCl (2.0 equiv) and PPh3 (2.2 equiv).

Central nervous system active compounds. V. Claisen rearrangement products of allyl vinyl ethers obtained from caprolactam derivatives

A series of allyloxy unsaturated tetrahydroazepinones has been prepared and their Claisen rearrangements have been investigated. The 4-allyloxy compounds (4a-e) rearranged thermally to give the 3-substituted hexahydro derivatives (9). In some cases further reaction products were obtained, particularly when higher temperatures were used. Rearrangement of the 4-propargyloxy system (4f) proved more complicated, and N-allyl-2,3,4,5-tetrahydro-1H-azepin-2-one derivatives (21a,b) were unreactive. Alkylation of the hexahydroazepine-2,4-dione system (3) with various allyl halides gave mixtures of the 3-mono-(20) and the 3,3-di-substituted (19) products. The unsaturated ethers generally showed marked muscular depression on the central nervous system of mice, while their rearrangement products were only weakly depressant.

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

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.

Claisen rearrangements—III : Convenient syntheses of the coumarins, osthenol, demethylsuberosin and coumurrayin

A simple 3-step method for the introduction of a 3,3-dimethylallyl unit ortho to a phenolic OH group is described. 7-Hydroxycoumarin, 1, was converted to its 1,1-dimethylallyl ether, 5, by reaction with 3-chloro-3-methylbutyne followed by partial hydrogenation. Pyrolysis of 5 gave mainly the C-8 Claisen rearrangement product, osthenol, 10, and also the C-6 isomer, 14. In a similar manner, coumurrayin, 13, was prepared from 5-methoxy-7-hydroxycoumarin in 57 % overall yield.

Benzodifurans. I. The synthesis of benzo[1,2‐b:5,4‐b]difuran and some methyl analogs

AbstractThe first parent benzodifuran (XVI) and three di‐ and trimethylated derivatives have been synthesized and screened for erythemal activity (negative response). Two benzodifurans were prepared from resorcinol and 2‐methylresorcinol by acetylation, Fries rearrangement, alkylation of the resulting 4,6‐diacetylresorcinols with ethyl bromoacetate, saponification, and then cyclization of the (4,6‐diacetyl‐1,3‐phenylenedioxy)diacetic acids. Another was prepared from the Claisen rearrangement product of 1,3‐bis(allyloxy)‐2‐methylbenzene by acetylation, bromina‐tion, and cyclization. Ozonolysis of the Claisen rearrangement product gave additional support to the formulation of o‐hydroxyphenylaeetaldehydes as cyclic hemiacetals. The parent benzodifuran was synthesized from 5‐formyI‐6‐hydroxybenzofuran, which was prepared in two steps from 5‐bromo‐6‐methoxybenzofuran. Alkylation of the former with ethyl bromoacetate, saponification, and cyclization furnished benzo[1,2‐b.5,4‐b ]difuran. The ultraviolet and nuclear magnetic resonance spectra of the four benzodifurans are compared.

Thermische Umwandlung von Phenyl‐penta‐2,4‐dienyläthern in 4‐[Penta‐2,4‐dienyl]‐phenole als Beispiel für [5,5]‐sigmatropische Umlagerungen. Vorläufige Mitteilung

AbstractThe reaction between phenol and trans penta‐2,4‐dienyl chloride gave trans penta‐2,4‐dienyl Phenyl ether (I), whereas with a mixture of sorbyl chloride and 1‐methylpenta‐2,4‐dienyl chloride, pure trans, trans hexa‐2,4‐dienyl phenyl ether (IV) and trans 1‐methylpenta‐2,4‐dienyl phenyl ether (V) were obtained. The ether I gave, on heating in dilute solution at 185°, 4‐(penta‐2,4‐dienyl)‐phenol (III) as the main product, and also some 2‐(2‐vinylallyl)‐phenol (II). The ether IV provided, on heating at 165°, in addition to the ortho CLAISEN rearrangement product VI, mainly a mixture consisting of 94% 4‐(1‐methylpenta‐2,4‐dienyl)‐phenol (VIII) and only 6% 4‐(hexa‐2,4‐dineyl)‐phenol(IX). The latter product (IX) was the only para isomer produced on heating ether V, but in addition 22% of the ortho rearrangement product VII was formed.The migrations I → III, IV → VIII, and V → IX, proceeding through a ten membered transition state, are the first [5,5] sigmatropic rearrangements described.

THE CLAISEN REARRANGEMENT IN AROMATIC HETEROCYCLIC COMPOUNDS. II. THE THERMAL REARRANGEMENT OF ALLYL 4-QUINOLYL ETHERS.

Thermal rearrangement of allyl 4-quinolyl ethers in 1-methylnaphthalene of without solvent resulted in the formation of good yields of the ortho-Claisen rearrangement products and small amounts of the lactim ehter-lactam isomerization products (1-allyl-4 (1H)-quinolones). A part of the Claisen rearrangement products were consecutively transformed into the 2, 3-dihydrofuro [3, 2-c] quinoline derivatives by their intramolecular cyclization in the process of this reaction. It was confirmed that the latter isomerization reaction is an intermolecular rearrangement.

STUDIES ON AZAINDOLIZINE COMPOUNDS. XVI. THE ALLYL REARRANGEMENT OF 7-ALLYLOXY-5,6-DIMETHYL-S-TRIAZOLO(1,5-A)PYRIMIDIME.

The thermal rearrangement of 7-allyloxy-5, 6-dimethyl-s-triazolo [1, 5-a] pyrimidine (III) was carried out and five kinds of rearrangement products ; 3- and 4-allyl-5, 6-dimethyl-s-triazolo [1, 5-a] pyrimidin-7 (3H and 4H) -ones (Ib and Ia), 5- (3-butenyl) -6-methyl-s-triazolo [1, 5-a] pyrimidin-7-ol (IV), and its 3- and 4-allyl derivatives (IVb and IVa) were obtained. Among these products, the out-of-ring Claisen rearrangement product (IV) was obtained in 66% yield. This reaction is the first example of out-of-ring migration of an allyl group to an active methyl group.