Fused Thiophenes and Some Oligomers and Polymers Therefrom - Thiophenes - page 167

O

C 6 H 13 B

O

C 6 H 13

S

S S

64

S S

Pd(PPh 3 ) 4

C 6 H 13

65

56

C 12 H 25

C 12 H 25 SnBu 3

S

S S

66

Pd(PPh 3 ) 4

S S

C 12 H 25

67

Scheme 16 Synthesis of 2,5-bis(5-hexylthien-2-yl)-TT (65) and 2,5-bis(5-dodecylthien-2-yl)-TT
(67)[ 37 ]

S S TBAF S

TMS
Pd(II), CuI

I I TMS TMS

S S S

THF

51% 81%

68 69 70

AcS I

S

AcS SAc

S

Pd(0), CuI

32% 71

H

P(O)(OEt) 2

S t -Bu

t -BuS

S

1) n -BuLi, DMF S

1 O

O

t -BuOK

2) t -BuLi, DMF

S S

t -BuS

17% H 78%

72 73

Scheme 17 Syntheses of rod-type oligomers 71 and 73 [ 38 ]

S

B(OH) 2

Pd(0)

S

75 ,56%

Br

S

Br

Br

S

Br

S

S

Br

74

S S B(OH) 2

S S

+

S S

Pd(0)

S S

Br

S

76 , 50% 77 , 15%

Scheme 18 Synthesis of tetrasubstituted TTs 75 and 76 [ 39 ]

a mechanically controllable break junction (MCBJ) technique, were achieved by
applying Sonogashira cross-coupling and Horner-Wadsworth-Emmons-
olefination protocols, respectively (Scheme 17 )[ 38 ].
Thieno[3,2- b ]thiophenes carrying either four phenyl (75) or four 2-thienyl
groups (76) were constructed using Suzuki cross-couplings of tetrabromo-TT (74)
with phenyl- or thiophene-2-boronic acids [ 39 ] Scheme 18 ).