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conferenceseries
.com
July 17-19, 2017 Chicago, USA
3
rd
International Conference on
Organic and Inorganic Chemistry
Volume 6, Issue 2 (Suppl)
Organic Chem Curr Res, an open access journal
ISSN:2161-0401
Organic Chemistry 2017
July 17-19, 2017
Organic Chem Curr Res 2017, 6:2 (Suppl)
DOI: 10.4172/2161-0401-C1-020
Carboranes and metallacarboranes: Advances and new perspectives
Narayan S Hosmane
Northern Illinois University, USA
M
ost of the carborane derivatives of the icosahedral (C
2
B
10
) or small cage (C
2
B
4
) systems are formed, by varying the
groups on the cage carbons. This is usually accomplished in the original carborane synthesis by reacting substituted
acetylenes with either the B
10
H
14
or B
5
H
9
precursors. These reactions led directly to the carbons adjacent carboranes in which
the carbon atoms occupy adjacent positions in the cage. The larger cages are obtained as
closo
-icosahedra, while the small
cage, C
2
B
4
-carboranes, have nido- structures. There is another geometry of the small cages in which the carbon atoms are
separated by a boron atom. Although these carbons apart or
nido
-2,4-(CR)
2
B
4
H
6
species are thermodynamically more stable
and are more symmetric than the carbons adjacent isomers, they are not as well studied. The main reasons for the relative
scarcity of information on the carbons systems lie in their method of preparation. They must be synthesized from their carbons
adjacent analogues through sequential oxidative cage closure/reductive cage opening reactions. The historic perspective of the
chemistry of carboranes and metallacarboranes with the latest findings in our research involving boron nanomaterials will be
presented in detail.
hosmane@niu.eduStille reaction of
β
-nitro and
β
-tosyl substituted styryl bromides
Antonio J Zapata V
Universidad de Guayaquil, Ecuador
T
he palladium-catalyzed coupling of organostannanes with organic electrophile (Stille reaction) has become an important
synthetic tool in organic chemistry (eq. 1). Several years ago, we became interested in applying the Stille reaction to
α-stannyl-α,
β
-unsaturated carboxylic esters. We found that these esters reacted with acid chlorides to afford good yields
of coupling products (eq. 2). However, the reaction failed when it was attempted with vinylic bromides or iodides. We
hypothesized that this result could be changed by reversing the roles of the reactants in the coupling process. Thus, a study
of the Stille coupling of a series of functionalized styryl bromides with 1-propenyltributyltin was undertaken (eq. 3). This
reaction afforded low to moderate yields of 1, 3-dienes. Interestingly, the best yield of product was obtained using methyl
α-bromocinnamate, the styryl bromide substituted with the more electron-withdrawing group (R=CO
2
Me). Consequently,
we decided to examine the Stille reaction of
β
-nitro and
β
-tosyl (
β
-(p-MeC
6
H
4
SO
2
)) substituted styryl bromides (eq. 4). The
β
-bromo-
β
-nitro-styrenes 1 and 2 reacted with a variety of organostannanes using
bis
(acetonitrile) dichloropalladium (II) as
catalyst and n-methyl-pyrrolidinone (NMP) as solvent at room temperature. Good yields of 2-nitro-1, 3-dienes were obtained
as a mixture of isomers. The Stille reaction of
β
-bromo-
β
-tosyl-styrenes 3 and 4 was also investigated. In this case, the best yields
of coupling products were obtained using an excess of organotin compound (1.5 equivalents), a mixture of
bis
(acetonitrile)
dichloropalladium (II) (5% molar) and copper iodide (10% molar) as catalysts and NMP as solvent at room temperature.
Again, good yields of products, as a mixture of isomers, were obtained. The Stille reactions of
β
-nitro and
β
-tosyl substituted
styryl bromides reported here constitute an useful synthetic tool towards the preparation of functionalized 1, 3-dienes. These
unsaturated molecules are among the most versatile organic compounds which participate in a wide variety of applications,
including fine chemical synthesis and polymer chemistry.
antonio.zapatav@ug.edu.ec