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ACS Catalysis
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The addition of molecular sieves, as described in the protocol originally reported by us (see ref. 3f), is
unnecessary if rigorously dried dioxane is employed.
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The ratio of the displacement constants KS(1a)/KS(1b) = 30 is of the same order of magnitude of the ratio
between the dissociation constants reported in Table 2, KD(1a)/KD(1b) = 57. This is to be expected, as these two
constants both mirror the affinity of the allene for Cu(I).
The two isomers are separable by standard flash chromatography on silica gel. This isomeric ratio is slightly
diminished if less than 4.0 equiv of amine are used, e.g. it is 82:8 for 2.0 equiv of morpholine.
Conversion of branched products similar to 3a to the linear isomer is known to take place with a Rhꢀbased
hydroamination catalyst in the presence of carboxylic acids, probably by the intermediacy of an η3ꢀallyl Rh(III)
complex: Chen, Q.ꢀA.; Chen, Z.; Dong, V. M. J. Am. Chem. Soc. 2015, 137, 8392ꢀ8395.
Under reaction conditions, copper can have a coordination number up to 4, as calculations for the formation of
[Cu(mp)n]+ point out (See the Supporting Information, section 1.4). The reaction of diethylamine and CuCl, for
instance, can give 1:1 or 2:1 complexes: (a) Clifton, J. R.; Yoke, J. T. Inorg. Chem. 1966, 5, 1630ꢀ1632. An
electrochemical study demonstrated that the maximum achievable coordination number for cationic
Cu(I)/amine complexes may be between 2 and 4 depending on the amine (e.g. it is 2 for piperidine and 3 for
butylamine and quinoline): (b) Chen, K.ꢀL. H.; Iwamoto, R. T. Inorganica Chim. Acta 1971, 5, 97ꢀ102. For
homogeneity and in order to make meaningful comparisons, tricoordinate geometries have been assumed
throughout all the calculations.
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Org. Biomol. Chem. 2010, 8, 3118ꢀ3127.
Cyclic allene 1c failed to give any detectable amount of hydroamination product, probably because of the easy
polymerization due to ring strain.
Assignment of the resonances of (E)-2c and (Z)-2c was done by comparison with published spectroscopic data:
Nishina, N.; Yamamoto, Y. Synlett 2007, 2007, 1767ꢀ1770.
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Brandsma, L. Synthesis of Acetylenes, Allenes and Cumulenes: Methods and Techniques (Best Synthetic
Methods); Elsevier Ltd.: Oxford, 2003; pp 323ꢀ326.
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Lu, T.; Lu, Z.; Ma, Z.ꢀX.; Zhang, Y.; Hsung, R. P. Chem. Rev. 2013, 113, 4862ꢀ4904.
Cu(NCMe)4(OTf) was selected for this screening because of its good solubility in all the solvent tested.
Primary aromatic or aliphatic amines are not reactive under our conditions employing Cu(NCMe)4PF6 as a
catalyst. For the goldꢀcatalyzed hydroamination of allenamides with anilines, see: Hill, A. W.; Elsegood, M. R.
J.; Kimber, M. C. J. Org. Chem. 2010, 75, 5406ꢀ5409.
Carbery, D. R. Org. Biomol. Chem. 2008, 6, 3455ꢀ3460.
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(a) Tsuda, M.; Kawasaki, N.; Kobayashi, J. Tetrahedron Lett. 1994, 35, 4387ꢀ4388. (b) Pouilhès, A.; Duvalꢀ
Lungulescu, M.; Lambel, S.; Léonce, S.; Langlois, Y. Tetrahedron Lett. 2001, 42, 8297ꢀ8299.
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