Addition/Correction pubs.acs.org/OrgLett
Cite This: Org. Lett. XXXX, XXX, XXX−XXX
Correction to “Copper-Catalyzed Direct Propargylation of Polyfluoroarenes with Secondary Propargyl Phosphates” Yan-Bo Yu, Zhi-Ji Luo, and Xingang Zhang* Org. Lett. 2016, 18 (13), 3302−3305. DOI: 10.1021/acs.orglett.6b01642 S Supporting Information *
relative configuration inversion product S-3d was produced in 45% yield with high enantioselectivity (98% ee) (Scheme 5a). This result clearly suggests that the SN1 pathway is not involved in the reaction. Surprisingly, treatment of S-2d with 1a in the presence of 12 or CuOAc (5 mol %) under standard reaction conditions led to a racemized 3d (Scheme 5b). Even with the reaction run at room temperature, a racemized product 3d was still observed in 15% yield (for details, see the Supporting Information). We envisioned that these results probably arose from the excess strong base t-BuOLi or the resulting pentafluorophenyllithium generated from reaction of t-BuOLi with 1a, which may racemize the starting material S-2d or the newly formed product S-3d. Accordingly, pentafluorophenyllithium was prepared by the reaction of 1a with t-BuOLi in THF at 40 °C for 2 h, which was then reacted with S-2d or S-3d in THF at 80 °C. It was found that S-3d can be easily racemized by the pentafluorophenyllithium (Scheme 5c), but S-2d was not (see Scheme S3b in the Supporting Information). In addition, when S-3d was treated with tBuOLi, a decreased ee value (83%) of S3d was also observed (Scheme 5d). However, no erosion of the enantioselectivity of S-2d was observed under the same reaction conditions (see Scheme S4a in the Supporting Information). Thus, these results demonstrate that a strong base can racemize the newly formed propargylated polyfluoroarenes (for details, see the Supporting Information). On the basis of these results and previous reports,7e a plausible reaction mechanism is proposed (Scheme 6). The reaction begins with the t-BuOLi-assisted direct cupration of polyfluoroarene 1 to produce polyfluoroarylcopper complex A. A subsequently undergoes oxidative addition with propargyl phosphate 2 to generate a configuration-inversed intermediate propargyl Cu(III) species B. Finally, stereoretentive reductive elimination of B delivers the propargylated polyfluoroarene, which can be easily racemized by the excess polyfluoroaryllithium or t-BuOLi under current reaction conditions to give a racemic mixture.” Reference 15 in the original text is revised as follows: “(15) For the detailed synthesis of enantiopure S-2d, see the Supporting Information.” Similarly, the configurations of 2d and 2da shown in the Supporting Information should also be corrected to S.
T
he absolute configuration of 2d was incorrectly assigned in the original paper. The correct absolute configuration of 2d should be S, and its correct structural drawing should be
The mistakes regarding the absolute configuration do not affect the validity of any of the reported yields, data, or information provided in the original manuscript and the Supporting Information. In addition, the results and conclusions of the Communication also remain valid. The authors sincerely apologize for any inconvenience this may have caused. Detailed corrections to Schemes 5a,b and 6, manuscript text, and Supporting Information are outlined below. Scheme 5. Mechanistic Studies
Scheme 6. Proposed Reaction Mechanism
The fourth to the second paragraphs from the bottom in the original manuscript text are revised as follows: “To gain some mechanistic insights into this reaction, a pentafluorophenyl copper complex C6F5Cu·(dioxane) 1214 and an optically pure S-2d (99% ee)15 were prepared. It was found that when S-2d was treated with 12 at room temperature, a © XXXX American Chemical Society
Received: March 5, 2018
A
DOI: 10.1021/acs.orglett.8b00683 Org. Lett. XXXX, XXX, XXX−XXX
Organic Letters
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Addition/Correction
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.orglett.8b00683. Revised file with corrected compound configurations (PDF)
B
DOI: 10.1021/acs.orglett.8b00683 Org. Lett. XXXX, XXX, XXX−XXX
