Synthesis and reducibility of homo-2-methoxyazocines and their benzo-fused derivatives. An examination of heteroatomic influences on the possible generation of 9C-10.pi. homoaromatic dianions

One hundred years of benzotropone chemistry

“…In 1978, in order to examine heteroatomic influences on the possible generation of 9C–10π homoaromatic dianions, Paquette’s group described the synthesis and reducibility of benzo-fused-homo-2-methoxyazocines from benzotropones ( Scheme 19 ) [ 87 ]. Firstly, dimethylsulfoxonium methylide addition to 4,5-benzotropone ( 11 ) provided the introduction of the cyclopropane ring required for two benzohomoazocines.…”

“…Benzohomoazocines 191 – 193 and benzomethoxyazocines 195 – 197 were prepared using a similar protocol illustrated in Scheme 18 and Scheme 19 ( Fig. 7 ) [ 84 – 87 145 ]. The cyclopropane ring in 192 was reduced to the corresponding dihydroazonine 193 .…”

A One-Pot Method to Prepare 4,5-Benzotropones and 2,3,4,5-Dibenzotropones

“…The yield of 3acould be improved to 81% by using 2,5 eq of BF3 . OEt2 (Table 1, entry 10), while utilization of the other solvents, such as DCE, , adjusting the reaction temperature to 0 o C or 45 o C (entry 11-15), and improving or reducing theequivalence of 2a (entry [16][17] were not helpful.…”

“…16 Further treatment of 10 with TsCl/Pyridine in DCM could provide a ring expansion product cyclooctene amide 11 in 52% yield. 17 Moreover, Baeyer−Villiger oxidation of 3f by using m CPBA as the oxidant afforded a rearrangement product 12 (Scheme 3). 10e Scheme 3 Further derivation of 2,3,4,5-dibenzotropone.…”

“…16 Further treatment of 10 with TsCl/pyridine in DCM provided the ring-expansion product cyclooctene amide 11 in 52% yield. 17 Moreover, Baeyer-Villiger oxidation of 3f by using mCPBA as the oxidant afforded the rearrangement product 12. 10e In addition, a cyclo-coupling reaction of 1a with 2a was performed on 2 mmol scale in DCM at rt, which provided 6phenyl-2,3,4,5-dibenzotropone (3a) in 69% yield (Scheme 5).…”