Chemistry Reference
In-Depth Information
H
O
N
O
7
N
N
O
O
EtO
Me
O
Gelsemine (
370
)
369
OMe
OMe
H
O
NH
O
O
N
N
t-
BuOCl,
CH
2
Cl
2
;
Na-Hg
MeOH
Et
2
O
Zn(OAc)
2
MeNO
2
373
(99%)
372
(85%)
371
SCHEME 10.58.
).
146
In contrast to
CVS-1778 (
383
374
, however, treatment of
379
with PIFA not only
led to the formation of
, which is thought to originate through
interception of the Wheland intermediate formed upon nitrenium ion attack.
Fortunately, aromatization of
381
, but also
380
380
was readily accomplished by treatment with
boron trifluoride and gave
in combined yield of 74%. In common with Romero,
Yang noted that addition of TFA to this cyclization lead to a small, but significant
increase in yield.
The nitrenium ion Ar
2
-7 annulation manifold has also been utilized by Tellitu
and Dom
ınguez for the preparation 1,4-benzodiazepin-2-ones.
147
For example,
381
Me
NHCO
2
Me
NHCO
2
Me
N
Cbz
PIFA, TFA
HN
O
N
O
N
CH
2
Cl
2
1 h, 0°C
OMe
OMe
HN
OMe
O
374
375
(85%)
376
Me
H
N
N
Cbz
Me
H
2
PIFA, TFA
N
N
CH
2
Cl
2
6 h, -5°C
Pd(OH)
2
/C
50°C, 48 h
N
N
H
O
MeO
O
377
(78%)
PNU-95666E (
378
) (84%)
SCHEME 10.59.
