Azidoiodinanes 2 and 4a,b can be prepared
from the appropriate benziodoxoles 1 and 3a,b and
trimethylsilyl
azide in the form of stable, crystalline compounds. A
single-crystal X-ray analysis for azide 4b revealed the
expected
hypervalent iodine distorted T-shaped geometry with the N1−I−O bond
angle of 169.5 (2) degrees. The lengths of
the bonds to the iodine atom, I−N (2.18 Å), I−O (2.13 Å), and
I−C (2.11 Å), are within the range of typical single
covalent bonds in organic derivatives of polyvalent iodine, while the
previously reported benziodoxoles generally
have an elongated I−O bond. The geometry of the
I(III)NNN fragment in 4b is similar to the
literature electron
diffraction data on monomeric iodine azide, IN3, in gas
phase. Azidobenziodoxoles 2,4 are potentially useful
reagents
for direct azidation of organic substrates, such as dimethylanilines,
alkanes, and alkenes. Reaction of 2 with
dimethylanilines proceeds under mild conditions to afford the
respective N-azidomethyl-N-methylanilines in
excellent
yield. Alkanes, cycloalkanes, and adamantanes react with
azidobenziodoxoles 2 or 4b in the presence of
radical
initiators at 80−132 °C with the formation of tertiary alkylazides,
while reaction of norbornane leads to exo-2-azidonorbornane. Under similar conditions cyclohexene is
selectively azidated at the allylic position.
Organosulfonyloxy derivatives of 1,2-benziodoxol-3(1H)-one (3a-c) and 3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole (5a-c) can be prepared in high yield by the reaction of 1-hydroxybenziodoxoles 1 or 4 and the corresponding sulfonic acids or Me(3)SiOTf in the form of stable, but moderately hygroscopic, microcrystalline solids. Reaction of the triflate derivatives 3a and 5a with alkynyltrimethylsilanes affords either alkynyliodonium triflates 6, or (E)-beta-(trifluoromethanesulfonyloxy)alkenyliodonium triflates 7, while the same reaction in the presence of pyridine selectively gives the respective 1-alkynylbenziodoxoles 8 and 9 in 82-90% yield.
A highly efficient one-pot procedure for 3-sulfenylation of 2-carboxyindoles is described. Treatment of thiols with N-chlorosuccinimide at -78 degrees C in CH(2)Cl(2) affords sulfenyl chlorides in situ that readily react with 2-carboxyindoles to give 3-thioindoles in high yields. This new method is milder, produces less waste, and is compatible with a wide range of thiol and indole functionality. [reaction: see text]
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1-(Organosulfonyloxy)-3(1H)-1,2-benziodoxoles: Preparation and Reactions with Alkynyltrimethylsilanes.-The 1-hydroxybenziodoxole (I) reacts with sulfonic acid derivatives to form a stable 1-sulfonyloxy derivative. This can be trapped in situ by the alkynylsilanes (IV) to yield the 1-alkynylbenziodoxoles (V) in the presence of pyridine. Omitting the pyridine results in formation of either the alkynyliodonium triflates (VI) or the alkenyliodonium compounds (VII). A similar sequence allows the synthesis of the triflate and the alkynyl derivative from bistrifluoromethylbenziodoxole (VIII). -(ZHDANKIN, V. V.; KUEHL, C. J.; KRASUTSKY, A. P.; BOLZ, J. T.; SIMONSEN, A.
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