Handbook of Functionalized Organometallics Applications in S

3.7 Synthesis and Reactions of Functionalized Alkyl Boron Derivates
3.7.5
Alkyl-Alkyl Suzuki Cross-coupling of Functionalized Alkyl Boranes with Alkyl
Bromides, Chlorides and Tosylates
Fu has developed an efficient cross-coupling of primary alkyl bromides (Eq.
1), [130] chlorides (Eq. 2) [131] and tosylates (Eq. 3) [132] with functionalized alkyl
boranes. The catalytic species are generated from Pd(OAc) 2 or [Pd 2(dba) 3] and
PCy 3 (for coupling of bromo and chloro alkanes). In the case of alkyl tosylates,
Pd(OAc) 2 and Pt-Bu 2Me gives the best results. This process takes advantage of the
high tolerance of organoboron derivatives with most functional groups that makes
this reaction a powerful synthetic tool (Scheme 3.85) [133].
NC-(CH 2) 6-Br MeO 2C(CH 2) 10(9-BBN)
t-BuCO 2(CH 2) 6-Cl
MeCO(CH 2) 6OTs
(1.2 equiv.)
BnO(CH 2) 5(9-BBN)
TESO(CH 2) 11(9-BBN)
Scheme 3.85 Alkyl-alkyl Suzuki cross-couplingof functionalized
alkylboranes with functionalized alkyl bromides, chlorides
and tosylates.
Pd(OAc) 2 (4 mol%)
PCy3 (8 mol%)
K3PO4·H 2O(1.2equiv.)
THF, 25 ºC
Pd2(dba) 3 (5 mol%)
PCy3 (20 mol%)
CsOH·H 2O (1.1 equiv.)
dioxane, 90 ºC
Pd(OAc) 2 (4 mol%)
PtBu2Me (16 mol%)
NaOH (1.2 equiv.)
dioxane, 50 ºC
3.7.6
Synthesis of Natural and Unnatural Amino Acids via B-alkyl Suzuki Coupling of
Functionalized Alkyl Boranes
MeO 2C(CH 2) 16CN
81 %
(eq.1)
BnO(CH 2) 11t-BuCO 2
65 %
(eq.2)
TESO(CH 2) 17COMe
55 %
Functionalized organoboron reagents of type 150, which are readily available from
serine via hydroboration of alkenes 151, undergo efficient Suzuki-coupling reactions
under mild conditions with a range of aryl and alkenyl halides [134]. These
adducts 152 are easily transformed into a variety of known and novel nonproteinogenic
N-protected amino acids via a one-pot hydrolysis-oxidation procedure leading
to amino acid derivatives such as 153. The methodology has been extended for
the synthesis of R,R-diaminopimelic acid (DAP) and R,R-2,7-diaminosuberic acid
(DAS) in enantiopure form (Scheme 3.86).
95
(eq.3)