sponding chromenes 16 and 17 resp. are obtained. Rcarrangcment of propargyl-and Z'-butinyl-lmethyl-2-naphthylether (6 and 7 resp.) in benzene at 80' in the presence of AgBF, gives the corresponding allenyl-naphthalenones 18 and 19 resp. Treatment of propargyl-and 2'-butinyl-mesitylether (8 and 9 resp.), and propargyl-and l'-mcthylpropargyl-2,6-dimethyl-phenylether (10 and 11 resp.) in benzene at 80" with AgRF, yiclds as the only product the corrcsponding 3-allcnylphenols 21, 22,24 and 25 (Scheme 3). It is shown that in thc prescnce of ~-tlichlor-dirhodiuni (1)tetracarbonyl in benzene a t 80" the ether 4 rcarranges to 2-methyl-2H-chromene (16). However with this catalyst the predominant reaction is a cleavage to phenol. No rcaction was observed when ethers 3 and 12 (Scheme 7 ) were trcated with thc tris-(trimethylsily1)-ester of vanadic acid in benzene a t 80" (see also [8]).By analogy with the known mechanism for thc silver catalysis of the reversible propargylcsterl allcnylester rearrangement [S], the silver (1)ion is assumcd to form a pre-equilibrium n-complex with the C, C-triplcbond of the substrate. This complex then undergoes a [3s, 3s]-sigmatropic rearrangerncnt (Scheme 2). I n the case of thc cthers 6, 7 and 12 the resulting allenyldienoncs merc isolated. The 2,G-dimethyl substituted ethers 8 , 9, 10 and 11 resp. first givc the usual allenyldienoncs (Schemu 3 ) . These then undergo a novcl silver catalysed dienon-phenol-rearrangemcnt (Sclzenzu4) to givc the 3-allcnylphcnols 21, 22, 24 and 25. Thc cthers 3, 4 and 5 with frcc orthopositions presumably rearrange first to the non-isolated 2-allcnyl-phenols 15, 42 and 43 resp.(Scheme 7). These then rearrange, either thermally or by silver (1)ion catalysis to the 2H-chromenes 13,16 and 17 resp. The rate of the rearrangerncnt of 2-allenylphenol (15) to 13 at room temperaturc in benzenc or chloroform is approximately doubled when silver ions are present as catalyst. 1. Einleitung. -Vor kurzem berichteten wir ausfiihrlich uber die durch Silberionen bewirkte, reversible Umlagerung von Propargylestern 1 in Allenylester 2 [5]. R4 1 2 Reaktionsschritt 2-Allenylphenol (15) gebildet, cfas dann durdi cine rasclie [I, 51-Wasserstoffverscliiebung und aiischliessencler Cyclisierung in 2 H-Cliromen (13)

Photochemical Cyclization of o‐, m‐, p‐Allylanisoles and o‐Allylanilines The compounds irradiated are summarized in Scheme 1. 2‐Allylaniline and N‐Alkyl Derivatives. Irradiation (ca. 3 h) of compounds 1–3 with a high pressure mercury lamp in benzene solution under argon (quartz vessel) gave in 40–80% yield the corresponding 2‐methylindolines 20, 22 and 25, respectively (Scheme 3). Tetrahydroquinolines (23, 26) were formed only in minor amounts (0,5%). Irradiation in methanol solution yielded in addition to the indolines the 2‐(2′‐methoxypropyl)‐anilines 21,24 and 27, respectively, in a ratio of ca. 0.3, 1.5 and 1.0 with respect to the indolines (Scheme 3). Similar results were obtained in ethanol solution. The observation that the photoreactions in benzene or methanol are not quenched by (E)‐piperylene or sensitized by acetone suggests that the transformation starts from the singlet manifold of the aniline chromophor. As outlined in Scheme 11 it is proposed that the excited molecules undergo an intramolecular electron transfer to give an acceptor(olefinic side chain)/donor(aniline part) complex (EDA complex; see [28]) of type {a,b} in which the positive charge is mainly located at the nitrogen atom and the negative charge at C(3′) of the allyl substituent. That the negative charge resides predominantly at C (3′) ‐ independently of alkyl substitution at C (3′) (see experiments cited in [26]) ‐ may be due to electrostatic attraction of the charges. Thus, the following H‐transfer occurs almost regiospecifically to give the singlet diradical c which cyclizes directly or via the spirocyclopropane derivative d to the indoline derivative 22. Intermediate d is also responsible for the formation of the 2′‐methoxypropyl compounds: It is suggested that in the polar solvent methanol d is partially converted to the zwitterion e, the immediate precursor of 24. Experiments with the deuteriated reactants N‐d‐2 and 2′‐d1‐2 (Scheme 3) are in agreement with the proposed mechanism. N, N‐Dialkyl‐2‐allylanilines and Allylanisoles. Upon irradiation in methanol or benzene, these aniline derivatives undergo cyclization to give as the only products the corresponding 2‐cyclopropylanilines in 50‐70% yield (Scheme 4). 2‐, 3‐ and 4‐ allylated anisoles behave in the same way on irradiation (Schemes 6‐8) as long as the allyl group carries no substituent (CH3, Cl) at the double bond (Schemes 9, 10). No photolytic cyclopropane ring formation is observed with the naphthalene derivatives 7, 8, 17 or 18 (Scheme 1). Experiments with the deuteriated compounds 2′‐d1‐4 and 1′, 1′‐d2‐11 ‐ synthesized according to Scheme 2 ‐ indicate that in all cases the cyclopropane formation occurs with concomitant 1,2 aryl migration (Schemes 5, 6) which characterizes the reaction as an aromatic di‐π‐methane rearrangement (Scheme 14). In contrast to the photoreactions described above the cyclopropane ring formation can be sensitized by acetone or quenched totally by (E)‐piperylene. A comparison of the triplet energies (ET) of the aromatic and olefinic chromophor of the...

Summavy. The allyl anisole derivatives 1, d2-l, 3, 5 and 7 (Scheme I ) , on exposure to UV. light in benzene, acetone or methanol solution, cyclize to yield the corresponding cyclopropyl anisole derivatives 2, d,-2, cis-and trans-4, 6 and 8, respectively. Under the above conditions the N, Ndialkyl-2-ally1 anilines 9, 10 and 11 give similar results (Scheme 2). On the other hand, N-alkyl-2-allyl anilines (15 and 19, Scheme 3) are transformed by UV. light in cyclohexane or benzene solution into 2-methyl-indolines (16 and 20, resp.), whereas in methanol solution the corresponding 2'-methoxy compounds 18 and 21 are formed in addition to 16 and 20, respectively.Very recently it was reported [2] that the photochemical cyclization of 2-and 4-ally1 anisole give 2-cyclopropyl (21% chemical yield) and 4-cyclopropyl anisole (25% chemical yield), respectively. This prompts us to publish our results which we have so far obtained in this field. These results are connected with earlier investigations on the photocyclization of 2-ally1 phenols to 2-methyl cumaranes and chromanes [3] (cj. also [4]).Irradiation (11 h) of 2-allyl-4-methyl anisole (1) in methanol solution with a mercury high pressure lamp (quartz vessel) under argon gave 2-cyclopropyl-4-methyl anisole (2)s) in a yield of 70Yo4) (quantum yield ca. 0,05) (Scheme 1). Similar yields were obtained when irradiations of 1 were performed in benzene of acetone solution. The l',l'-dideuterio anisole derivative d,-1 afforded on exposure to UV. light in methanol solution exclusively d,-2 with both deuterium atoms at C(2'). Irradiation of 4-methyl-2-(lf-methylallyl) anisole (3) in benzene solution led to a 2,4: 1 mixture of 4-methyl-2-(2'-cis-and 2'-trans-methyl-cyclopropyl) anisole (cis-and trans-4) 6, in a yield of 80%.The photocyclization of 4-allyl-2,6-dimethyl anisole (5) did not occur as well as that of the previously mentioned 2-allylated species: After irradiating 5 for 50 h some starting material was still present. 4-Cyclopropyl-2,6-dimethyl anisole (6) was isolated by preparative gasphase chromatography (prep. GC.) in a yield of 20%. Most ineffective was the photocyclization of 3-ally1 anisole (7) : The time of irradiation had to be

Die UV‐Bestrahlung der Anisole (I) in Benzol liefert die Cyclopropylanisole (II).

No abstract