Nitrile Oxides, Nitrones, and Nitronates in Organic Synthesis : Novel ...

Me
N
O N
Mes
R
N
Me
162
REACTIONS OF NITRILE OXIDES 53
O N
The 1,3-dipolar cycloaddition of 1,5-benzodiazepine to a nitrile oxide occurs
at the N=C double bond at the 1 and 2 positions of the benzodiazepine system
(331, 332). A second nitrile oxide molecule adds at the C(4)=N(5) bond
(333). Behavior of 1,5-benzothiazepines is similar to that of 1,5-benzodiazepines.
3a,4,5,11-Tetrahydro-1,2,4-oxadiazolo[4,5-d][1,5]benzothiazepines 163 (X = S,
R 1 = Ph, 2-, 3-, 4-ClC6H4, 4-MeOC6H4, Me,R 2 = Ph, 4-MeOC6H4, 4-MeC6H4,
4-FC6H4, R 3 = Ph, 3-BrC6H4, CO2Et) and 3a,4,5,11-tetrahydro-6H-1,2,4oxadiazolo[4,5-d]
[1,5]benzodiazepines 163 (X = NH) were obtained by 1,3dipolar
cycloaddition reactions of 2,3-dihydro-1,5-benzothiazepines and
2,3-dihydro-1H-1,5-benzodiazepine with benzonitrile oxides, respectively
(332, 334).
X
R 3
N
163
R 1
Mes
R 2
O
N
1.3.4.2.3. Nitrogen-containing Hetarenes Reactions of RCNO (R = 2,6-
Cl2C6H3, 2,4,6-Me3C6H2) with cycloalkano[b]indoles 164 (n = 1, 2, 3) gave
mainly the oxadiazolo[4,5-a]indoline adducts 165. The structure elucidation of
the adducts was based on their spectral data, chemical behavior and in the case
of 165 (R = 2,6-Cl2C6H3, n= 1) by X-ray analysis (335). The suggested mechanism
takes into account the ability of 2,3-disubstituted indoles, especially, of
1,2,3,4-tetrahydrocarbazoles, to autooxidation and proposes the intermediate formation
of compounds 166 which react with nitrile oxides to give the Þnal products
165 (335).
Mesitonitrile oxide, but not benzonitrile oxide, adds to aza-analogs of phenanthrene,
viz., benzo[h]quinoline, 1,10-, 1,7-, and 4,7-phenanthrolines to give low
yields of mono-cycloadducts at the C(5)=C(6) bond. Only 4,7-phenanthroline gave
minor products, of which one the bisadduct 167 was isolated in approximately 7%
yield. Phenanthridine reacts with two nitrile oxides but affords phenanthridin-6one
rather than a cyclo-adduct (336).