Preparation, structure, and reactivity of bicyclic benziodazole: A new hypervalent iodine heterocycle

Article abstract of DOI:10.3762/BJOC.14.87

A new bicyclic organohypervalent iodine heterocycle derivative of benziodazole was prepared by oxidation of 2-iodo-N,N'-diiso-propylisophthalamide with m-chloroperoxybenzoic acid under mild conditions. Single crystal X-ray crystallography of this compound revealed a five-membered bis-heterocyclic structure with two covalent bonds between the iodine atom and the nitrogen atoms. This novel benziodazole is a very stable compound with good solubility in common organic solvents. This compound can be used as an efficient reagent for oxidatively assisted coupling of carboxylic acids with alcohols or amines to afford the corresponding esters or amides in moderate yields.

Full text of DOI:10.3762/BJOC.14.87

Preparation, structure, and reactivity of bicyclic benziodazole:
a new hypervalent iodine heterocycle
Akira Yoshimura*1,2, Michael T. Shea2, Cody L. Makitalo2, Melissa E. Jarvi2,
Gregory T. Rohde3, Akio Saito4, Mekhman S. Yusubov1 and Viktor V. Zhdankin*1,2
Full Research Paper
Open Access
Address:
Beilstein J. Org. Chem. 2018, 14, 1016–1020.
1The Tomsk Polytechnic University, 634050 Tomsk, Russia,
2Department of Chemistry and Biochemistry, University of Minnesota,
Duluth, MN 55812, USA, 3Marshall School, Duluth, MN 55811, USA,
and 4Division of Applied Chemistry, Institute of Engineering, Tokyo
University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei,
Tokyo 184-8588, Japan
doi:10.3762/bjoc.14.87
Received: 06 February 2018
Accepted: 20 April 2018
Published: 08 May 2018
This article is part of the Thematic Series "Hypervalent iodine chemistry in
organic synthesis".
Email:
Akira Yoshimura* - ayoshimu@d.umn.edu; Viktor V. Zhdankin* -
vzhdanki@d.umn.edu
Guest Editor: T. Wirth
* Corresponding author
© 2018 Yoshimura et al.; licensee Beilstein-Institut.
License and terms: see end of document.
Keywords:
benziodazole; biheterocycles; hypervalent iodine; iodine; oxidatively
assisted esterification
Abstract
A new bicyclic organohypervalent iodine heterocycle derivative of benziodazole was prepared by oxidation of 2-iodo-N,N’-diiso-
propylisophthalamide with m-chloroperoxybenzoic acid under mild conditions. Single crystal X-ray crystallography of this com-
pound revealed a five-membered bis-heterocyclic structure with two covalent bonds between the iodine atom and the nitrogen
atoms. This novel benziodazole is a very stable compound with good solubility in common organic solvents. This compound can be
used as an efficient reagent for oxidatively assisted coupling of carboxylic acids with alcohols or amines to afford the correspond-
ing esters or amides in moderate yields.
Introduction
In recent years, the interest in heterocyclic organohypervalent are commonly employed as efficient electrophilic atom-transfer
iodine compounds has experienced an unprecedented growth reagents useful for conversion of various organic substrates to
[1-6]. A variety of new hypervalent iodine heterocycles have the corresponding products of azidation [7-11], amination
been prepared, and numerous reactions employing these com- [12,13], cyanation [14-17], alkynylation [18-20], or chlorina-
pounds as reagents for organic synthesis have been reported. tion [21,22]. Recently, Zhang and co-workers reported the prep-
The benziodoxole-based five-membered iodine heterocycles aration of several bicyclic benziodoxoles 3 starting from
represent a particularly important class of hypervalent 2-iodoisophthalic acid (2, Scheme 1b). These bicyclic benz-
iodine(III) reagents. Substituted benziodoxoles 1 (Scheme 1a) iodoxoles 3 can be used as efficient coupling reagents for the
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Beilstein J. Org. Chem. 2018, 14, 1016–1020.
Scheme 1: Representative examples of benziodoxoles and benziodazoles.
direct condensation reaction between carboxylic acids and alco- efficient azidation reagent with a reactivity similar to azido-
hols or amines to provide esters, macrocyclic lactones, or benziodoxoles [33]. Recently, the Wang group reported a
amides and peptides [23-25].
rhenium catalyst-mediated oxidative dehydrogenative olefina-
tion of a C(sp3)–H bond using acetoxybenziodazole reagents
Numerous examples of five-membered hypervalent iodine(III) [36]. To the best of our knowledge, all known benziodazoles
heterocycles containing other than oxygen heteroatoms, such as have a mono-heterocyclic structure, and bi-heterocyclic benz-
sulfur [26], boron [27,28], phosphorous [29], or nitrogen iodazole derivatives similar to the bicyclic benziodoxole 3 have
[30-32], have been synthesized and characterized by X-ray never been reported. In this paper, we report the synthesis,
crystallography. In particular, several nitrogen containing structural characterization, and reactivity of a novel bicyclic
heterocyclic iodine(III) compounds 5, benziodazoles, have been benziodazole derivative 7 (Scheme 1d).
reported by Gougoutas [31], Balthazor [32], and our group
[33-35] (Scheme 1c). X-ray structural studies of these benzioda- Results and Discussion
zoles confirmed the presence of covalent bonding between An obvious approach to the preparation of bicyclic benzioda-
iodine and nitrogen atoms in the heterocyclic ring. Benzioda- zoles 7 involves the oxidation of the corresponding 2-iodo-
zoles 5 are usually prepared by the treatment of 2-iodobenz- N,N’-dialkylisophthalamides 6 (Scheme 1). We have synthe-
amide derivatives 4 with appropriate oxidants under mild condi- sized the precursors 6 in two simple steps starting from
tions [31-35]. Derivatives of benziodazole can be used as commercially available 2-iodoisophthalic acid (2). Firstly,
reagents for various oxidative functionalizations of organic sub- 2-iodoisophthalic acid (2) was converted to the corresponding
strates [33,36]. For example, azidobenziodazole was used as an acyl chloride 8 by treatment with thionyl chloride (Scheme 2).
Scheme 2: Preparation of bicyclic benziodazole 7a.
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Beilstein J. Org. Chem. 2018, 14, 1016–1020.
In the second step, acyl chloride 8 reacted with appropriate
alkylamines to give the corresponding 2-iodo-N,N’-di-
alkylisophthalamides 6 in good yields. The oxidation of 2-iodo-
N,N’-diisopropylisophthalamide (6a) with m-chloroperoxy-
benzoic acid (mCPBA) under mild conditions afforded the
desired bicyclic benziodazole 7a in good yield. Unfortunately,
we could not obtain the corresponding pure benziodazole deriv-
atives 7 by the oxidation of precursors 6b or 6c under similar
conditions. According to NMR spectra of the reaction mixture
of 6b or 6c, the desired products 7b or 7c were observed in the
reaction as a complex mixture with other compounds. Bicyclic
benziodazole 7a is a thermally stable, white, microcrystalline
compound that can be stored in a refrigerator for several weeks.
Solutions of 7a in CDCl3 or CD3CN did not show any decom-
position even after storage for over one month at room tempera-
ture.
Figure 1: X-ray crystal structure of compound 7a. Ellipsoids are drawn
to the 50% probability level. Selected bond lengths and angles:
I(1)–C(1) 2.040 (4) Å; I(1)–N(1) 2.184 (4) Å; I(1)–N(1) 2.177 (4) Å;
N(1)–I(1)–C(1) 76.89 (18)°; N(2)–I(1)–C(1) 77.02 (18)°; N(1)–I(1)–N(2)
153.90 (15)°.
The solid state structure of compound 7a was characterized by
X-ray crystallography. A single crystal X-ray diffraction of 7a
confirmed the bicyclic benziodazole structure with two cova- Similar to the iodosodilactone reagents [23-25], the bicyclic
lent bonds between the iodine atom and the nitrogen atoms benziodazole 7a could be expected to be a useful reagent for
I(1)–N(1) = 2.184 (4) Å, I(1)–N(2) = 2.177 (4) Å (Figure 1). oxidatively assisted coupling reactions. Previously, Zhang and
These bond lengths are similar to previously reported benzioda- co-workers reported the reactions of carboxylic acids with alco-
zole structures [29-32]. According to X-ray crystallography hols or amines in the presence of stoichiometric amounts of
data, structure 7a has a distorted T-shaped geometry with an iodosodilactones 3 forming the corresponding esters or amides
N(1)–I(1)–N(2) angle of 153.90 (15)°. Compared to other re- in moderate to good yields via an oxidatively assisted coupling
ported bicyclic hypervalent iodine compounds [23,25,37], this reaction [23-25]. We have investigated the analogous oxidative-
is the most bent structure at the N(1)–I(1)–N(2) angle. An addi- ly assisted coupling reaction of carboxylic acids 9 with alco-
tional relatively weak intermolecular coordination between the hols 10 or amine 12 using benziodazole 7a under similar condi-
iodine atom and the oxygen atom of a neighboring molecule tions (Scheme 3). The reaction of butyric acid (9a) with benzyl
(I(1)···O’(1) = 3.107 (3) Å) results in the overall pseudo-square alcohol (10a) using benziodiazole 7a in the presence of tri-
planar geometry at the iodine center.
phenylphosphine and N,N-dimethyl-4-aminopyridine (DMAP)
Scheme 3: Benziodadiazole 7a mediated oxidatively assisted esterification and amidation reactions.
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Beilstein J. Org. Chem. 2018, 14, 1016–1020.
ORCID® iDs
in chloroform solution under reflux conditions afforded the
desired product 11a in good yield. As expected, the reactions of
benzoic acid (9b) with benzyl alcohol (10a) or 1-pentanol (10b)
under the same conditions gave the corresponding esters 11b or
11c in moderate yields (Scheme 3, reaction 1). The analogous
reaction of butyric acid (9a) with benzylamine (12) and benz-
iodazole 7a under similar conditions produced the expected
amide 13 in moderate yield (Scheme 3, reaction 2). Compared
to the iodosodilactone reagents 3 [23-25], benziodazole 7a
showed a comparable or better reactivity. In contrast to
iodosodilactone, benziodazole 7a has excellent solubility in
chloroform allowing reactions in solution under homogeneous
conditions. Similar to the reactions of iodosodilactone 3,
Ph3P=O and amide 6a were observed as the byproducts in these
reactions (Scheme 3), which is in agreement with the previ-
ously proposed mechanism of oxidatively assisted esterifica-
tion or amidation [23,38].
Akira Yoshimura - https://orcid.org/0000-0002-2577-397X
Gregory T. Rohde - https://orcid.org/0000-0001-7787-8012
Akio Saito - https://orcid.org/0000-0002-8291-2059
Mekhman S. Yusubov - https://orcid.org/0000-0001-9233-1824
Viktor V. Zhdankin - https://orcid.org/0000-0002-0315-8861
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