The Diels-Alder reaction represents a promising tool for use in
asymmetric synthesis. The reaction involves a rigid transition state
that facilitates the formation of one diastereomeric transition state
and is reversible. This satisfies two necessary criteria for
asymmetric synthesis.
The Diels-Alder reactions of 1,l-dialkylspiro[2.4]-4,6- heptadienes
with maleic anhydride and p-benzoquinone...
The tosylhydrazones of exo-3-deuteriocamphor and 2- deuterio-2,4-dimethy1-3-pentanone were treated with Nbromosuccinimide (NBS) and pyruvic acid to regenerate the parent ketones. The ketones from the pyruvic acid cleavage show a significant loss of deuterium. The ketones from the NBS cleavage show no loss of deuterium, indicating that stereochemical integrity at. C[subscript...
The photochemistry of aldicarb and two related compounds,
0-(methylcarbamoyl) isobutyraldehyde oxime and 0-(methylcarbamoyl)
trimethylacetaldehyde oxime was explored under laboratory
conditions. Upon irradiation aldicarb decomposed rapidly to
methylamine, dimethylamine, tetramethylsuccinonitrile, and
1-methylthio-2, 3-dicyano-2, 3-dimethylbutane. The other two
compounds decomposed only after a long period of irradiation. The
difference in reactivity was...
Intramolecular cyclization of organometallic compounds represents
a promising tool for synthesis in general. The use of strategically-
placed heteroatoms in the cyclizing molecule can influence
the stereochemistry and/or efficiency of an organometallic cyclization
while providing for functionality in the cyclic product.
The work described herein first concerns cyclizations of organolithiums....
The tosylhydrazones of 2-heptanone, 4,4-dimethy1-2-
heptanone, 6-heptyn-2-one and 4,4-dimethy1-6-heptyn-2-
one were synthesized and decomposed under a variety of
reaction conditions: dry lithium and sodium salt pyrolyses,
sodium methoxide thermolyses in diglyme and photolyses of
the lithium salt in tetrahydrofuran. The saturated analogues
2-heptanone tosylhydrazone and its 4,4-dimethyl
isomer afforded the...
The photochemistry of some analogs of insect growth regulators
(IGR's) was studied. Methyl geranate, TY, was synthesized and the
mechanisms of its photochemical reaction pathways were studied by a
variety of techniques. Direct irradiation of 71 in ether leads to the
formation of five new products: 98, the product of...
The effect of the conjugation with cyclopropyl rings
on the activation parameters for the formation of
carbenes from the corresponding diazo compounds was
investigated using diisopropylcarbene (46), cyclopropyl-isopropylcarbene
(47), and dicyclopropylcarbene (48).
Each of these three carbenes was generated by the
thermolysis of the parent benzenesulfonylhydrazone
potassium salts using DMSO...
Photolysis of pentachlorobenzene was carried out in the absence
of an electron donor species at 254 nm in cetyltrimethylammonium
bromide surfactant solution. The results are consistent with the
excited triplet undergoing homolytic cleavage of a C-Cl bond in
competition with formation of the excimer, in which the radical anion
undergoes...
The photodebromination of selected bromoarenes has been studied at 300 nm
to determine the the possible mechanistic pathways leading to product.
Irradiation of 4-bromobiphenyl (BpBr) at this wavelength leads to the product
biphenyl. The quantum yield of intersystem crossing (0.98) and quenching
studies with cis-1 ,3-pentadiene suggest that the reaction...
Several experiments were undertaken to investigate the mechanism of
photodechlorination of pentachlorobenzene. The thermal methoxydechlorination
reaction of pentachlorobenzene was studied. In DMSO at 50 °C sodium
methoxide reacts smoothly with pentachlorobenzene to give three
tetrachloroanisole isomers. A second-order kinetic plot for this reaction is linear to
high precision, indicating that...
The photohydrodebromination of brominated paracyclophanes was studied to
help elucidate the possible mechanistic pathways leading to product for
bromoarenes in general. Several brominated [2.2]paracyclophanes were studied to
determine the effect of substitution patterns on this reaction. [2.2]Paracyclophanes
were chosen for this study in order to investigate possible intramolecular excimer
formation...
Polyhalogenated benzenes have been analyzed by standard electron capture
chemical ionization mass spectrometry (ECCI/MS), and electron monochromator mass
spectrometer (EM/MS) systems. The EM/MS experiments distinguished electronegative
compounds (especially isomers) by transient negative ions (TNIs) of the same mass but
differing energies and/or the formation of distinct TNIs of different masses...
The principal salinity extrema and extremum surfaces of the
world ocean are described by the analysis and plotting of data from
885 hydrographic stations in the three major oceans, the Southern
Ocean, and the American Mediterranean Sea. The distributions of
salinity, temperature, depth, and density along the extremum surfaces,
plotted...