Correction pubs.acs.org/acscatalysis
Correction to Enhanced Catalytic Performance of Indenediide Palladium Pincer Complexes for Cycloisomerization: Efficient Synthesis of Alkylidene Lactams Noel Á ngel Espinosa-Jalapa, Diandian Ke, Noel Nebra, Lucas Le Goanvic, Sonia Mallet-Ladeira, Julien Monot, Blanca Martin-Vaca,* and Didier Bourissou* ACS Catal. 2014, 4, 3605−3611. DOI: 10.1021/cs5010322 S Supporting Information *
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alkyne. As a substitute, a cyclization reaction has been carried out on 1a-D deuterated at the alkyne position (CCD, 93% of isotopic labeling) (Scheme 1). No deuterium scrambling was detected, and the obtained lactam 2a-D was selectively deuterated cis to the NTs group.
age 3607, Table 2, entry 8 and Table 3. Follow-up experiments in our laboratory have shown that structures proposed for compounds 2h, 2i, and 2j on the basis of NMR analyses were incorrect. The structures of 2h, 2i-O-endo, 2i-Nendo, and 2j-O-endo drawn below have been established by Xray diffraction analyses:
Scheme 1. Cycloisomerization of Deuterium-Labelled 4Pentynoic Acid 1a-D
As a consequence, the last two paragraphs of the “Cycloisomerization of N-Tosyl alkynylamides” section need to be corrected as follows: “To extend further the scope of the reaction, we then turned our attention to internal N-tosyl alkynylamides, which are substantially more difficult to cyclize than terminal substrates.16a,22 Cyclization of 1h required heating at 90°C (instead of 60°C for the corresponding terminal alkyne 1a), but reaction was complete within 24 h (entry 8). 6-Endo cyclization affords the unsaturated 2-piperidone 2h (83% isolated yield), whose structure was proved by XRD. Rigid internal substrates such as 1i and 1j were also investigated (Table 3). Complex III was found to efficiently promote the cycloisomerization of 1i at 50 °C. The conversion is complete within 5 h and occurs exclusively via 6-endo cyclization. However, on the contrary to what was observed for the previous alkynylamides, competition between O- and Ncyclization occurs.1 For 1i and 1j, the product deriving from Ocyclization is major (O-/N-cyclization ratio: 84/16 for 1i and 92/8 for 1j, 92% overall yield). The structures of these products were determined by X-ray diffraction (see Supporting Information). To discard a potential catalyst effect, the cyclization of 1i and 1j with complexes Ia,c was carried out. Lower conversions were observed (∼50%, entries 1, 2, and 5, Table 3), and decomposition of Ia,c into free ligand was detected by 31P NMR. However, the reaction proceeds again exclusively via 6-endo cyclization with comparable O-/Ncyclization ratio to those obtained with III, indicating only minimal influence of the catalyst structure on selectivity.” Page 3608 The Z stereochemistry of 2h-exo was used as experimental proof for trans nucleophilic attack of the amide to the activated © 2016 American Chemical Society
Taking into account this result, the (ii) alinea of the “Mechanistic Considerations” section has to be modified as follows: “(ii) Cyclization by nucleophilic attack of the nitrogen atom on the CC bond would then give the alkenyl complex B. Trans addition is supported by the Z stereochemistry of the product 2a-D obtained by 5-exo cyclization of the deuterated alkyne 1a-D.” Only the structures of compounds 2h, 2i, and 2j are different from those proposed initially, and we apologize for any inconvenience caused by these errors. The structures of lactams 2a, 2b, and 2g have been unambiguously confirmed by X-ray diffraction studies. The corrections do not change the fact that the new SCS indenediide Pd pincer complexes have enhanced catalytic performance and enable the efficient cyclization of Ntosylalkynylamides and challenging alkynoic acids.
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ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acscatal.6b00198. Crystallographic data for 2a (1446628), 2b (1446630), 2g (1446625), 2h (1438982), 2i-O-endo (1446629), 2iN-endo (1446628), and 2j-O-endo (1446626) (CIF) Check CIF/PLATON report (PDF) Published: February 3, 2016 1565
DOI: 10.1021/acscatal.6b00198 ACS Catal. 2016, 6, 1565−1566
Correction
ACS Catalysis
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REFERENCES
(1) For references in which O-/N-cyclization competition is reported, see: (a) Campbell, M. J.; Toste, F. D. Chem. Sci. 2011, 2, 1369−1378. (b) Gimeno, A.; Cuenca, A. B.; Medio-Simon, M.; Asensio, G. Adv. Synth. Catal. 2014, 356, 229−236. (c) Preindl, J.; Jouvin, K.; Laurich, D.; Seidel, G.; Fürstner, A. Chem. - Eur. J. 2016, 22, 237−347.
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DOI: 10.1021/acscatal.6b00198 ACS Catal. 2016, 6, 1565−1566
