Upload
morgan-obrien
View
219
Download
0
Embed Size (px)
Citation preview
Dr. Kristoffer Rem Labing-isaMassachusetts Institute of Technology
Nitro Group Structure
N double bonded to O
and also single
bonded to O and to an R.
Background
Often highly explosive, especially when the
compound contains more than one nitro group.one of the most common
explosophores (functional group that makes a
compound explosive) used globally.
Background
The NO2 group is called as nitro group. It is electron
withdrawing group due to its -Inductive effect as well as -
Resonance effect. The structure of NO2 group is
given below.
Background
Trinitrotoluene,
best known as a useful explosive
material with convenient handling
properties
Nomenclature
Nitromethane Nitrobenzene
Aliphatic Nitro
Aromatic Nitro
Name the longest and continuous carbon chainName the –NO2 compound as a
–nitro substituent
Nomenclature
2-methyl-3-nitrobutane
Nitro butane
1-nitronaphthale
ne
Physical Properties
colorless liquids with pleasant smell, sparingly
soluble in water, have high boiling points. Most of nitro alkanes are quite stable and
can be distilled without decomposition, and they are polar due to the presence of
nitro group
Aliphatic Nitro
Physical Properties
yellow color liquids which intensified to brown by time
color with characteristic odor, steam volatile and can
be purified by steam distillation and they are polar due to the presence of nitro
group
Aromatic Nitro
Chemical Properties
Nitro compounds undergo tautomerism in solution to
azinitro form, which is acidic in nature. Hence, all the nitro
compounds are weakly acidic in nature.
Aliphatic Nitro
Chemical Properties
Nitro benzene is electron withdrawing group by both
inductive effect and resonance effect. Hence it
deactivates the benzene ring and it is meta directing
group.
Aromatic Nitro
Preparation
CH3-CH3 + HNO3/H2SO4 → CH3-CH2-NO2
By direct nitration of alkanes
nitroethane
nitrobenzene
ethane
benzene
Preparation
By treating amines with alkaline KMnO4
nitromethaneaminomethane
Nitro Journal
α-Fluoro-α-nitro(phenylsulfonyl)meth
ane as a fluoromethyl pronucleophile:
Efficient stereoselectiveMichael addition to
chalcones
G. K. Surya Prakash1, Fang Wang, Timothy Stewart, Thomas Mathew, and George A. Olah1
Introduction
Enantioselective preparation of fluoromethylated organics is one of the major areas of
interest today because fluoromethyl
substituted compounds carry great importance in
pharmaceutical chemistry, material science and
healthcare
IntroductionOne of the major recent
developments in this area involves the efficient, and
highly enantioselective monofluoralkylation of
alcohols using the Mitsunobu reaction
IntroductionOur recent investigations
showed that fluorine containing (phenylsulfonyl)methane derivatives such as -nitro,
cyano, ester, or acetyl-substituted
fluoro(phenylsulfonyl)methane can be effectively used under
mild conditions for the synthesis of a variety of
functionalized monofluoromethylated
compounds, which are crucial synthons for many valuable
compounds in the pharmaceutical arena
Introduction
IntroductionVery recently, Shibata and
colleagues haveachieved a catalytic
enantioselective Michael addition of FBSM to chalcones using cinchona-based phase
transfer catalysts.
Michael addition between nitromethane
and chalcone with high ee and chemical yields
using cinchona alkaloid-derived chiral bifunctional thiourea asan
effective organocatalyst.
Introduction
Preliminary screening of
the catalysts
was carried out using
dichloromethane or
toluene as solvent.
Introduction
We have screened a series ofcatalysts for the
enantioselective addition of -fluoro--nitro-
(phenylsulfonyl)methane (FNSM) to chalocones
systematically and we found that catalysts enable this
reaction to occur successfully in the absence
of any baseto provide exclusive 1,4-
addition products
Discussion
IntroductionFNSM has been
added to a series of chalcone
derivatives to obtain the
corresponding adducts in high yields with high diastereomeric
ratios and excellent
enantiomeric excesses
Discussion
The bifunctional catalysts
themselves are capable of
deprotonating the FNSM into the corresponding
carbanion, which can attack the
Michael acceptors in an appropriate configuration by undergoing an
inversion
Discussion
The absolute configuration of the product was unequivocally
established by X-ray crystallographic analysis
Methods
To a solution of -fluoro--nitro(phenylsulfonyl) methane (21.9 mg, 0.1 mmol, 1 equivalent)
and ketone (0.2 mmol, 2 equivalent) in CH2Cl2, Et3N (10.0 L of 0.1 mmol, 0.7
equivalent) was added. The reaction mixture was stirred for 12 h at room temperature and the conversion was monitored by 19F NMR before purification (diastereomeric ratios were 1:1 in all of the cases). The
reaction mixture was loaded on to a preparative TLC plate. In most cases, the
diastereomers can be separated with hexane/ethyl acetate (4/1– 6/1) to produce the title product in good to excellent yield.
Typical Procedure for Catalytic 1,4-Addition of
-Fluoro--nitro(phenylsulfonyl) methane to ,-Unsaturated Ketones.
Methods
To a solution of -fluoro--nitro(phenylsulfonyl) methane (21.9 mg, 0.1 mmol, 1 equivalent)
and ketone (0.2 mmol, 2 equivalent) in precooled toluene (20 °C, 0.5 mL), catalystQNI was added (6.0 mg, 0.01 mmol, 10 mol%) in
one load. The reaction mixture was stirred for 1 min and placed in freezer (20 °C) for 2 days without stirring. The reaction mixture was monitored by 19F NMR for conversion and
diastereoselectivity, and loaded on to preparative TLC plate. In most cases, the
diastereomers can be separated with hexane/ethyl acetate (4/1– 6/1) to produce the title product in good to excellent yield. Products
were characterized by spectral analysis (1H NMR, 13C NMR, 19F NMR, and HRMS), and the
ee values were determined by chiral HPLC.
Typical Procedure for Catalytic Enantioselective 1,4-Addition of
-Fluoro--nitro- (phenylsulfonyl)methane to Chalcones.
Conclusion
In conclusion, we have achieved an enantioselective
and diastereoselective1,4-conjugate addition of
FNSM, an effective fluoromethyl pronucleophile to chalcones using cinchona alkaloid based bifunctional
catalysts with highest efficacy observed for QN I.