Page 680 - Advanced Organic Chemistry Part B - Reactions & Synthesis

Visual models and additional information on Dialkylzinc Addition can be found 655
in the Digital Resource available at: Springer.com/carey-sundberg.
SECTION 7.3
Aryl zinc reagents are considerably more reactive than alkylzinc reagents in these Organometallic
Compounds of Group
catalyzed additions to aldehydes. 151 Within the same computational framework, phenyl IIB and IIIB Metals
transfer is found to have about a 10 kcal/mol advantage over ethyl transfer. 152 This
is attributed to participation of the orbital of the phenyl ring and to the greater
electronegativity of the phenyl ring, which enhances the Lewis acid character of the
catalytic zinc.
R′
Zn O H

O Zn
R

Aspects of the scale-up of aminoalcohol-catalyzed organozinc reactions with
aldehydes have been investigated using N,N-diethylnorephedrine as a catalyst. 153 In
addition to examples with aromatic aldehydes, 3-hexanol was prepared in 80% e.e.

OH
NEt 2
Ph
CH 3
CH (CH ) CH O + (C H ) Zn CH (CH ) CHCH CH 3
2 5 2
2
2 2
3
2 2
3
OH
80% e.e.
Additions to aldehydes are also catalyzed by Lewis acids, especially Ti i-OPr 4
and trimethylsilyl chloride. 154 Reactions of
-, -, -, and -iodozinc esters with
benzaldehyde are catalyzed by Ti i-OPr Cl. 155
3
Ti(i-OPr) Cl
3
) CO C H
)
PhCH O + IZn(CH 2 n CO C H PhCH(CH 2 n 2 2 5
2 2 5
OH
n % yield
2 90*
3 88*
4 80
5 95
* product is lactone

151
C. Bohm, N. Kesselgruber, N. Hermanns, J. P. Hildebrand, and G. Raabe, Angew. Chem. Int. Ed. Engl.,
40, 1488 (2001); C. Bohm, J. P. Hildebrand, K. Muniz, and N. Hermanns, Angew. Chem. Int. Ed. Engl.,
40, 3284 (2001).
152
J. Rudolph, T. Rasmussen, C. Bohm, and P.-O. Norrby, Angew. Chem. Int. Ed. Engl., 42, 3002 (2003).
153 J. Blacker, Scale-Up of Chemical Processes, Conference Proc., 1998; Chem. Abstr., 133, 296455 (2000).
154 D. J. Ramon and M. Yus, Recent Res. Devel. Org. Chem., 2, 489 (1998).
155
H. Ochiai, T. Nishihara, Y. Tamaru, and Z. Yoshida, J. Org. Chem., 53, 1343 (1988).