Zinkchloridkatalysierte, thermische Umlagerungen von N‐Allyl in C‐Allyl‐aniline; ladungsinduzierte, aromatische Amino‐Claisen‐Umlagerungen

Abstract

N-Allyl-2-methylaniline (12) forms on heating at 140" in xylene in the presence of zinc chloride 2-allyl-6-methylaniline (19) as major compound and 4-allyl-2-methylaniline (20) as well as 2,7-dimethyl-indoline (21) as minor products. Compound 21 is also formed when 19 is heated in the presence of zinc chloride (schcme 2). That 19 arises from a chargc-induced [3 s, 3s) sigmatropic rearrangement of 12 -and 20 from two consecutive [3s, 3s]-sigmatropic transformationsfollows from the reaction of N-crotyl-2-niethylanilinc (13) in the presence of zinc chloride at 140". 2-(l'-Methylallyl)-6-methylanilinc (22) and 4-crotyl-2-mcthylaniline (23) are formed cxclusively. Small amounts of 2.3.7-trimethyl-indoline (24) and 2-(czs-and trans-1'-methylpropenyl)-6-methylaniline (cis-and tralzs-25) are observed as by-products. Compound 24 arises from 22 in the presence of zinc chloride (scheme 3 ) . Similar results are obtained when N-allyland N-(2'-methylallyl)-N-methyl-aniline (14 and 15, respectively) are heated in the presence of zinc chloride. Whercas 14 gives nearly exclusively 2-allyl-N-rncthyl-aniline (28) and only small amounts of the corresponding 1,2-dimethyl-indoline (29) and of 2-(cisand trans-propeny1)-Nmethyl-aniline (cis-and trans-27), 15 forms comparable amounts of 2-(2'-methylallyl)-N-mcthylaniline (30), 1,2,2-trimethyl-indoline (31), and 2-isobutenyl-N-methyl-aniiiline (32) (schcme 4). Compound 30, and also 32, are transformed into 31 on heating in the presence of zinc chloride.Chargc-induced aromatic amino-Claisen rearrangemcnts are also observed when N-allylated anilininm tetraphenylborates are heated a t 100-105' in hexamethyl phosphoric acid triamide. Thus, N-allyl-and N-crotyl-N, N-dimethyl-aniliniuni tetraphenylborate (16 and 17, rcspectively) yicld 2-allyl-and 2-(1'-mcthylally1)-N, N-dimethyl-aniline (33 and 34, respectively) besides small amounts of N, gives, besides appreciable amounts of N, N-dimethyl-aniline, a mixture of Z-(l'-phenylallyl)-, 2-cinnamyl-, and 4-cinnamyl-N, N-dimethyl-aniline (35, 36, and 37, respectively) in which the first two compounds predominate.Teil der geplantrn Dissertation J1. Sckmid, Universitiit Zurich. Das Ringspannung aufwcisende l-$-Bromphenyl-2-isopropenylazirldiIi wird schon bei 140 ' in hoher Ausbeutc in 7-Brom-4-methyl-2,5-diliydro-(l-benzazepin) umgcwandelt [3], z,

Catalysis of the Cope and Claisen rearrangements

“…The [3,3]-sigmatropic nature of the process was later demonstrated in the conversion of the IV-crotyl derivative, 265 (R = Me) (1 equiv of ZnCl2, xylene, 140 °C, 4.5 h) in 69% overall yield to a mixture containing 78% ortho product, 266,12% para product, 267, as well as small amounts of material (4% 268, 2% 269, 4% 270) derived respectively from cyclization or isomerization of 266, and cleavage of 265. 175 The noninverted crotyl 268 269 270 group in 267 is consistent with two sequential [3,3] rearrangements. In the reaction under similar conditions of iV-allyl-2-methylaniline, 265 (R = H), there was formed in 70% combined yield a mixture consisting of 81% 266, 10% 267, 8% 268, and 1.5% 270.…”

Regioselective Palladium(II)-Catalyzed Synthesis of Five- or Seven-Membered Ring Lactones and Five-, Six- or Seven-Membered Ring Lactams by Cyclocarbonylation Methodology

“…2-Allylphenol ( 1a ), 6-methyl-2-allylphenol ( 1b ), and 4-chloro-2-allylphenol ( 1c ) are commercially available. The following 2-allylphenols, 2-aminostyrenes, and 2-allylanilines are known compounds prepared according to literature procedures and have spectral properties in accord with literature data: 1d , 1e , 1f , 1g , 1h , 1i , 5a , 5c , 5e , 5f , 5g−j , 8a , 8b , 8c , , 8e , , 8f , 8g , and 8h …”

A Cope Rearrangement in the Reaction Catalyzed by Dimethylallyltryptophan Synthase?

“…Enzymes that have been proposed to catalyze pericyclic reactions are somewhat rare and include examples such as chorismate mutase, − precorrin-8x methyl mutase, , isochorismate pyruvate lyase, , and the Diels–Alderases. − While the jury is still out on DMAT synthase, the observed formation of compound 1 , combined with the structural analysis of the Michaelis complex and the intrinsic reactivity of the indole ring, leads us to consider a Cope rearrangement mechanism as a real possibility for this enzyme. Although pericyclic rearrangements have long been proposed to play roles in the biosynthesis of the indole alkaloids such as ergotamine and echinulin, ,,,,− mechanistic evidence using purified enzymes has been largely absent until now.…”