Allenols versus Allenones: Rhodium‐Catalyzed Regiodivergent and Tunable Allene Reactivity with Triazoles

Abstract

2-Pyrrolines and 6-oxo-hexa-2,4-dienals have been prepared through the divergent reactions of 1-benzenesulfonyl-4-aryl-1,2,3-triazoles with functionalized allenes. The rhodium-catalyzed reactions between allenols and 1-benzenesulfonyl-4-aryl-1,2,3-triazoles yielded 2-pyrrolines. This transformation is compatible with the presence of aliphatic, aromatic, heterocyclic, amide, and halogen functional groups. Interestingly, a reactivity switch took place when the allene-tethered alcohol substrate was replaced by its ketone counterpart. When the rhodium-catalyzed reaction of 1-benzenesulfonyl-4-phenyl-1,2,3-triazole was performed with allenones, acyclic 6-oxo-hexa-2,4-dienals were stereoselectively formed as (2Z,4E) isomers.

Chemoselectivity Switching in the Rhodium‐Catalyzed Reactions of 4‐Substituted‐1‐sulfonyl‐1,2,3‐triazoles with Allenols: Noticeable Differences between 4‐Acyl‐ and 4‐Aryl‐Triazoles

“…[2] Markedly contrasting results were obtained in comparison with donor/acceptor carbenoids. [6] Based on these results, we believed that allenols might also act as an O-containing nucleophiles able to trap acceptor/ acceptor carbenoids. [4] Recently, Miura and Murakami have described the metal-catalyzed reac-tion of 4-aryl-1-tosyl-1,2,3-triazoles with simple allenes to form pyrroles or a,b,g,d-unsaturated imines (Scheme 1b), [5] while we reported the transannulation reaction of 4-aryl-1-tosyl-1,2,3-triazoles with allenols to give 2-pyrrolines (Scheme 1c).…”

“…[4] Recently, Miura and Murakami have described the metal-catalyzed reac-tion of 4-aryl-1-tosyl-1,2,3-triazoles with simple allenes to form pyrroles or a,b,g,d-unsaturated imines (Scheme 1b), [5] while we reported the transannulation reaction of 4-aryl-1-tosyl-1,2,3-triazoles with allenols to give 2-pyrrolines (Scheme 1c). [6] Based on these results, we believed that allenols might also act as an O-containing nucleophiles able to trap acceptor/ acceptor carbenoids. Herein, we describe an unprecedented O-attack/reorganization sequence between allenols and 4-acyl-1-tosyl-1,2,3-triazoles leading to 3methylene-5,6-dioxo-hept-1-enyl-4-amine derivatives (Scheme 1d).…”

“…On the other hand, dramatic growth in the synthetic utility of allenes has been noticed in the last decade . Recently, Miura and Murakami have described the metal‐catalyzed reaction of 4‐aryl‐1‐tosyl‐1,2,3‐triazoles with simple allenes to form pyrroles or α,β,γ,δ‐unsaturated imines (Scheme b), while we reported the transannulation reaction of 4‐aryl‐1‐tosyl‐1,2,3‐triazoles with allenols to give 2‐pyrrolines (Scheme c) . Based on these results, we believed that allenols might also act as an O ‐containing nucleophiles able to trap acceptor/acceptor carbenoids.…”

“…mmol) of allenol 1 c, and after chromatography of the residue, gave compound 3 c (78 mg, 50%) as a green solid; mp 106-108 8C; 1 HÀNMR (300 MHz, C6 D 6 , 258C) d: 7.67 (d, 2H, J = 8.3 Hz, ArH), 7.00 (m, 4H, ArH), 6.69 (d, 2H, J = 8.0 Hz, ArH), 5.94 (d, 1H, J = 1.0 Hz, =CH), 5.88 (d, 1H, J = 9.8 Hz, CHÀNH), 5.61 (d, 1H, J = 9.8 Hz, CHÀNH), 5.01 (d, 1H, J = 1.2 Hz, CHH), 4.85 (s, 1H, CHH)From 78 mg (0.40 mmol) of allenol 1 d, and after chromatography of the residue, gave compound 3 d (58 mg, 35%) as a green oil; 1 HÀNMR (300 MHz, C 6 D 6 , 258C) d: 7.60 (d, 2H, J = 8.3 Hz, ArH), 7.17 (s, 1H, ArH), 7.02 (d, 1H, J = 7.7 Hz, ArH), 6.94 (d, 1H, J = 8.9 Hz, ArH), 6.80 (t, 1H, J = 7.8 Hz, ArH), 6.64 (d, 2H, J = 8.0 Hz, ArH), 5.89 (s, 1H, =CH), 5.58 (d, 1H, J = 10.0 Hz, CHÀNH), 5.36 (d, 1H, J = 9.9 Hz, CHÀNH), 4.85 (d, 1H, J = 1.2 Hz, CHH), 4.78 (s, 1H, CHH), 1.80 (s, 3H, Me), 1.77 (d, J = 1.5 Hz, 3H, Me), 1.68 (s, 3H, Me); 13 CÀNMR (75 MHz, C 6 D 6 , 258C) d: 195.5 (C=O), 194.0 (C=O), 143.5, 142.8, 139.0, 137.6, 137.5, 134.4, 129.8 (Ar, 2CH), 129.0 (Ar, CH), 128.1 (Ar, CH), 127.8 (Ar, CH), 127.7 (Ar, CH), 127.3 (Ar, 2CH), 126.9 (Ar, CH), 119.4 (=CH 2 ), 58.0 (CHÀNH), 25.8 (Me), 23.4 (Me), 21.1 (Me); IR (C 6 H 6 , cm À1 ): n 3273, 1718, 1596, 1160; HRMS (ES): calcd for C 22 H 26 ClN 2 O 4 S [M + NH 4 ] + : 449.12963; found: 449.13153. (Z)-N-(1-(2-Methoxyphenyl)-2-methyl-3-methylene-5,6-dioxohept-1-en-4-yl)-4-methylbenzenesulfonamide 3 e. From 72 mg (0.378 mmol) of allenol 1 e, and after chromatography of the residue, gave compound 3 e (61 mg, 37%) as a green oil; 1 HÀNMR (300 MHz, C 6 D 6 , 258C) d: 7.65 (d, 2H, J = 8.3 Hz, ArH), 7.32 (dd, 1H, J = 7.5, 1.1 Hz, ArH), 7.01 (t, 1H, J = 12.5 Hz, ArH), 6.80 (t, 1H, J = 7.4 Hz, ArH), 6.65 (d, 2H, J = 8.0 Hz, ArH), 6.50 (m, 2H, ArH +=CH), 5.64 (q, 2H, J = 4.3 Hz, CHÀNH), 4.97 (s, 1H, CHH), 4.93 (s, 1H, CHH), 3.41 (s, 3H, OMe), 1.78 (s, 3H, Me), 1.77 (d, 3H, J = 1.5 Hz, Me), 1.73 (s, 3H, Me); 13 CÀNMR (75 MHz, C 6 D 6 , 258C) d: 195.8 (C=O), 194.4 (C=O), 157.2, 143.2, 143.1, 137.9, 136.1, 130.4 (Ar, CH), 129.7 (Ar, 2CH), 128.8 (=CH), 127.3 (Ar, 2CH), 126.5, 125.8 (Ar, CH), 120.7 (Ar, CH), 119.2 (=CH 2 ), 110.9 (Ar, CH), 58.2 (CHÀNH), 55.0 (OMe), 25.3 (Me), 23.5 (Me), 21.1 (Me); IR (C 6 H 6 , cm À1 ): n 3270, 1718, 1597, 1160; HRMS (ES): calcd for C 23 H 26 NO 5 S [M + H] + : 428.15262; found: 428.15404. d, 1H, J = 9.8 Hz, CHÀNH), 5.69 (d, 1H, J = 9.8 Hz, CHÀNH), 5.46 (d, 1H, J = 1.2 Hz, CHH), 5.05 (s, 1H, CHH), 1.81 (s, 3H, Me), 1.51 (s, 3H, Me); 13 CÀNMR (75 MHz, C 6 D 6 , 25 8C) d: 194.8 (C=O), 194.4 (C=O), 143.5, 140.4, 140.1, 139.9, 137.3, 135.1, 133.8, 130.9 (Ar, 2CH), 130.5 (Ar, 2CH), 129.8 (Ar, 2CH), 128.9 (Ar, 2CH), 128,1 (Ar, CH), 128.0 (= CH), 127.7 (Ar, 2CH), 127.4 (Ar, 2CH),121.6 (=CH 2 ), 58.9 (CHÀNH), 23.1 (Me), 21.1 (Me); IR (C 6 H 6 , cm À1 ): n 3263, 1719, 1596, 1159; HRMS (ES): calcd for C 27 H 28 ClN 2 O 4 S [M + NH 4 ] + : 511.14528; found: 511.14537. mmol) of allenol 1 g, and after chromatography of the residue, gave compound 3 g (64 mg, 49%) as a yellow oil; 1 HÀNMR (300 MHz, C 6 D 6 , 258C) d: 7.58 (d, 2H.…”

Metal-mediated synthesis of pyrrolines

“…Alcaide and Almendros group reported a rhodium-catalyzed synthesis of 2-pyrrolines 303 from 1-benzenesulfonyl-4-aryl-1,2,3-triazoles 302 with allenols 301 (Scheme 105). 150 The protocol makes use of 1 mol% of Rh 2 (oct) 4 in toluene at reux to obtain a separable mixture of 2-pyrrolines 303 (only the mayor diastereoisomer is shown) with yields in the range of 31-73% (R 2 s H). When R 1 is aromatic, the diastereoselectivities were modest (d.r.…”