ISSN:
0018-019X
Keywords:
Chemistry
;
Organic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
Reactions of monosubstituted alkenes RCH = CH2 and [Re(η5-C5H5)(CH2Cl2) (NO)(PPh3)]+BF4- give complexes ([Re(η5-C5H5))(CH2=CHR)(NO) (PPh3)]+BF4- (1a-g) in 63-99% yields as mixtures of (RS,SR)- and (RR,SS)-diastereoisomers (1a (R = Me), 66:34; 1b (R = Pr), 63:37; 1c (R = PhCH2), 70:30; 1d (R = Ph), 75:25; 1e (R = i-Pr), 64:36; 1f (R = t-Bu), 84:16; 1g (R = Me3Si), 69:31; Scheme 2). These differ in the C=C enantioface bound to the chiral Re fragment. In most cases, the analogous reactions of RCH=CH2 and [Re(η5-C5H5) (C6H5Cl)(NO)(PPh3)]+ BF4+ give comparable results. When 1a-e, g are heated in PhCl at 95-100°, equilibration to 96:4, 97:3, 97:3, 90:10, 〉 99:〈 1, and 〉 99:〈 1 (RS,SR)/(RR,SS) mixtures occurs (79-99% recoveries; Tables 1 and 2). Thus, thermodynamic enantioface-binding selectivities are much higher than kinetic binding selectivities. This phenomenon is analyzed in detail. A crystal structure of (RS,SR)-1e (monoclinic, P21/c, a = 10.256(1) Å. b = 17.191(1) Å, c = 16.191(1) Å, β = 101.04(1)°, Z = 4) shows that the Re-C(1)-C(2) plane (see Fig.2) is nearly coincident with the Re-P bond (angle 15°), and that the i-Pr group is ‘syn’ to the nitrosyl ligand.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/hlca.19920750204
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