COMMUNICATIONS
ꢀ
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2002, 31, 298; b) B. J. Cowen, L. B. Saunders, S. J.
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[4] a) N. W. Mszar, F. Haeffner, A. H. Hoveyda, J. Am.
Chem. Soc. 2014, 136, 3362–3365; b) H. Wu, F. Haeff-
ner, A. H. Hoveyda, J. Am. Chem. Soc. 2014, 136,
3780–3783.
[5] For selected examples of processes employing Rh-
boron exchange, see: a) T. Hayashi, K. Ueyama, N. To-
kunaga, K. Yoshida, J. Am. Chem. Soc. 2003, 125,
11508–11509; b) T. Hayashi, M. Takahashi, Y. Takaya,
M. Ogasawara, J. Am. Chem. Soc. 2002, 124, 5052–
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K. Ueyama, R. Shintani, T. Hayashi, J. Am. Chem. Soc.
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R. Shintani, T. Hayashi, Org. Lett. 2005, 7, 307–310;
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Chem. Soc. 2007, 129, 5336–5337; i) R. B. C. Jagt, P. Y.
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Minnaard, Angew. Chem. 2006, 118, 2855–2857; Angew.
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cursors for the formation of enantioenriched C C
bonds.
Experimental Section
General Procedure A for the Rh-Catalyzed
Allenylation of Sulfonylimines
To an 8-mL vial with magnetic stir-bar was sequentially
charged ligand (5.2 mol%), chlorobis(ethylene)rhodium
dimer (2.0 mol%), imine (1 equiv.), propargyl boronate
(2 equiv.), and toluene (0.25M) in a glove-box under an N2
atmosphere. The mixture was allowed to stir for 10 min.
Then, a freshly prepared and degassed 0.5M solution of
KOH in water (6.0 mol%) was added followed by ethanol
(1.1 equiv.). The vial was capped, removed from the glove-
box, and heated to 808C for 6 h. The mixture was cooled to
room temperature, and 0.2 mL of 2M HCl was charged, fol-
lowed by 2 mL of water. The mixture was extracted with
EtOAc (2ꢂ5 mL), and the combined organic layers were
dried with Na2SO4 and concentrated under vacuum. The
crude residue was then purified by flash chromatography on
silica gel (Biotage, hexanes/EtOAc mixtures). Enantioselec-
tivity was determined by chiral HPLC analysis.
General Procedure B for the Rh-Catalyzed
Allenylation of Sulfonylimines
To an 8-mL vial with magnetic stir-bar was sequentially
charged ligand (5.2 mol%), chlorobis(ethylene)rhodium
dimer (2.0 mol%), imine (1 equiv.), propargyl boronate
(2 equiv.), and toluene (0.25M) in a glove-box under an N2
atmosphere. The mixture was allowed to stir for 10 min.
Then, a freshly prepared and degassed 0.5M solution of
KOH in water (6.0 mol%) was added followed by ethanol
(1.1 equiv.) and stirred for 5 min. Proton sponge (1 equiv.)
was then added. The vial was capped, removed from the
glove-box, and heated to 608C for 6 h. The mixture was
cooled to room temperature, and 0.2 mL of 2M HCl was
added, followed by 2 mL of water. The mixture was extract-
ed with EtOAc (2ꢂ5 mL), and the combined organic layers
were dried with Na2SO4 and concentrated under vacuum.
The crude residue was then purified by flash chromatogra-
phy on silica gel (Biotage, hexanes/EtOAc mixtures). Enan-
tioselectivity was determined by chiral HPLC analysis.
[6] J. D. Sieber, D. Chennamadhavuni, K. R. Fandrick, B.
Qu, Z. S. Han, J. Savoie, S. Ma, L. P. Samankumara, N.
Grinberg, H. Lee, J. J. Song, C. H. Senanayake, Org.
Lett. 2014, 16, 5494–5497.
[7] For propargylation/allenylation reactions employing
catalyst-boron exchange, see: a) D. R. Fandrick, K. R.
Fandrick, J. T. Reeves, Z. Tan, W. Tang, A. G. Capacci,
S. Rodriguez, J. J. Song, H. Lee, N. K. Yee, C. H. Sena-
nayake, J. Am. Chem. Soc. 2010, 132, 7600–7601;
b) K. R. Fandrick, D. R. Fandrick, J. T. Reeves, J. Gao,
S. Ma, W. Li, H. Lee, N. Grinberg, B. Lu, C. H. Sena-
nayake, J. Am. Chem. Soc. 2011, 133, 10332–10335;
c) D. R. Fandrick, J. T. Reeves, J. M. Bakonyi, P. R.
Nyalapatla, Z. Tan, O. Niemeier, D. Akalay, K. R. Fan-
drick, W. Wohlleben, S. Ollenberger, J. J. Song, X. Sun,
B. Qu, N. Haddad, S. Sanyal, S. Shen, S. Ma, D. Byrne,
A. Chitroda, V. Fuchs, B. A. Narayanan, N. Grinberg,
H. Lee, N. Yee, M. Brenner, C. H. Senanayake, J. Org.
Chem. 2013, 78, 3592–3615; d) D. R. Fandrick, C. S.
Johnson, K. R. Fandrick, J. T. Reeves, Z. Tan, H. Lee,
J. J. Song, N. K. Yee, C. H. Senanayake, Org. Lett. 2010,
12, 748–751; e) D. R. Fandrick, K. R.; Fandrick, J. T.
Reeves, Z. Tan, C. S. Johnson, H. Lee, J. J. Song, N. K.
Yee, C. H. Senanayake, Org. Lett. 2010, 12, 88–91;
f) D. R. Fandrick, J. Saha, K. R. Fandrick, S. Sanyal, J.
Ogikubo, H. Lee, F. Roschangar, J. J. Song, C. H. Sena-
nayake, Org. Lett. 2011, 13, 5616–5619; g) K. R. Fan-
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