Kinetics of Formation of Propylenediaminetetraacetatocobaltate(III) from the Corresponding Pentadentate Complexes

Reaction of allylic boron and aluminum "ate" complexes with organic halides and carbonyl compounds. Trialkylboranes as regio-, stereo-, and chemoselective control elements

“…Sterically more hindered B(í-Bu)3 and less hindered «-Bu-9-BBN are not effective, indicating that the steric circumstances between these two extremes are important for the transition state leading to the threo product. Further, the reaction of ate complexes proceeds with greater threoselectivity than that of the corresponding trivalent crotylborane (11). These results suggest that the enhancement of the threoselectivity via the tetravalent boron is ascribed to two factors: (i) the geometry of crotyl unit is fixed predominantly to trans through the prevention of the allylic rearrangement;7 (ii) the transition state (TJ of the tetravalent boron…”

“…The reaction of various allylic halides with several allylic boron ate complexes was examined to establish a high generality of control of regiochemistry (Table II). As mentioned later, 13C NMR spectra of lithium crotyl-9-BBN ate complex clearly indicate that 1-methylallyl isomer is not involved (entries [7][8][9][10][11].26…”

“…In other words, the selectivity of 7 is enhanced by the control of high reactivity of 7 via the ate complexes. On the other hand, the reactivity of 11 is enhanced through the ate complexes.…”

“…3-Methyl-1,5-hexadien-3-ol:71 bp 57-59 °C (45mmHg); IR (cm"1, CC14) 3300, 1640, 990, NMR (CC14) 1.40 (3 H, s), 2.30 (2 H, d, J = 7 Hz), 4.80-5.20 and 5.56-6.04 (4 H and 2 H, allyl H); mje (M+) 112. 1-Phenyl-1,5hexadien-3-ol:72 bp 70 °C (ImmHg); IR (cm"1, CC14) 3300,1640,1600, 995, 960, 910; NMR (CC14) 2.35 (2 H, t, / = 7 Hz), 2.40 (1 H, b s, OH), 4.95-5.20 and 5.60-6.00 (2 H and 1 H, allyl ), 6.20 (1 H, dd, / = 7 and 16 Hz), 6.35 (1 H, d, / = 16 Hz), 4.25-4.50 (1 H, m), 7.10-7.40 (5 H, m); mje (M+) 11,1980 Abstract: 180-tracer studies show that cyclization of cis-[Co(en)2(OH2)(glyOH)]3+ and cw-[Co(en)2(OH2)(glyO)]2+ (glyOH = N-bound glycine; glyO = N-bound glycinate) to give [Co(en)2(glyO)]2+ containing chelated glycinate occur intramolecularly without displacement of coordinated water. The rates of these reactions are relatively fast with t\¡2 at 40 s at pH 0-1 and Z,/2 ca 400 s at pH 4; the overall rate law takes the form kobsi = (&h[H+]2 + kii'K1 [H+] + fcOHA1A2)/(A,A2 + fc,[H+] + [H+]2) with kH = 1.9 X 10™2 s™1, kH' = 1.05 X 10™3 s'1, koli = 1.74 X 10'5 s™1, pA, = 2.3, pA2 = 6.3 at 25.0 °C, and µ = 1.0 (NaC104).…”