Handbook of Functionalized Organometallics Applications in S

Br O
X
Br O
R 2
R 2
O
85: X = Si-tBu 2
86: X = CPh2
R 1 R 1
O
O
O
O
O
11.3 Reactions of Higher Nuclearity Chromium and Tungsten Carbenes
1) n BuLi
2) Cr(CO) 6
3) Me 3OBF 4
X
48 %
89 R 1 = Et R 2 = Et X = Sit Bu2
90 R 1 = Et R 2 = Et X = CPh 2
91 R 1 = n Pr R 2 = H X = CPh 2
92 R 1 = Oct R 2 = H X = CPh 2
or
(CO) 5Cr
(CO) 5Cr
13 - 39 %
R 1
R 2
R 2
O
OMe
OMe
1) R
2) CAN
1
Scheme 11.27 Bisquinone functionalization of heterohelicenes
via bidirectional benzannulation: Bisangular versus
angular-linear annulation.
O
O
R 1
87, 88
O
R 2
O
X
O
93 R 1 = t Bu R 2 = H X = Sit Bu2
94 R 1 = n Pr R 2 = H X = Sit Bu 2
95 R 1 = t Bu R 2 = H X = CPh 2
Double benzannulation can be applied to the diastereoselective synthesis of
biaryls. Upon reaction with diphenylbutadiyne the biscarbene complex 96 bearing
aC 2-symmetric (2R,3R)-butane-2,3-diol bridge affords a single R,R,S-diastereomer
of the tethered 2,2¢-binaphthol 97 in moderate yield (Scheme 11.28) [53].
(CO) 5Cr O O Cr(CO) 5
96
Ph Ph
THF, 75ºC
23 %
HO Ph
H
O O
97
O
O
H
X
Ph OH
Scheme 11.28 Diastereoselective biaryl synthesis via double benzannulation.
469