E. Teso Vilar

A facile synthesis of new homochiral β-amino alcohols with norbornane framework

Abstract New homochiral 1,2-amino hydroxy derivatives of norbornane are easily prepared starting from naturally occurring 2-norbornanones.

Synthesis of homochiral 3-substituted cyclopentanones from 2-norbornanones

Abstract The cleavage of the C 1 -C 2 bond in norbornane derivatives is accomplished by base-promoted hydrolysis of α-nitroketones, periodate oxidation or Beckmann fragmentation of suitable precursors prepared from the 2-norbornanones 1 . These reactions are the basis for the synthesis of the 3-substituted homochiral cyclopentanones 6 , 10 or 15 .

Synthesis of homochiral 1,2-diols from (−)-fenchone and (+)-camphor

Abstract (+)-(1 R ,2 S )-1,2-dihydroxy-7,7-dimethylnorbornane ( 3 ) and (−)-(1 R ,2 R )-1,2-dihydroxy-3,3-dimethylnorbornane ( 12 ) have been obtained from (−)-fenchone and (+)-camphor.

On the mechanism of the Leuckart reaction. Enantiospecific preparation of (1R,2R)- and (1S,2S)-N-(3,3-dimethyl-2-formylamino-1-norbornyl)acetamide

Abstract The Leuckart reaction of 2-norbornanone and (1 R )- N -(3,3-dimethyl-2-oxo-1-norbornyl)acetamide ent - 1b furnishes the expected N -(2-norbornyl)formamides 11 and ent - 10 in good yield. Surprisingly, under the same reaction conditions, the (1 R )- N -(7,7-dimethyl-2-oxo-1-norbornyl)acetamide 1a gives only 10 , the enantiomeric form of the product obtained from ent - 1b . An explanation of these results is given and a reaction mechanism, based on an unprecedented intramolecular transamidation, is proposed.

Synthesis of homochiral cyclopentane derivatives by Beckmann fragmentation of 1-substituted 2-norbornanones

Abstract The fragmentation of 2-norbornanone oximes 2 was achieved by reaction with Tf2O/pyridine under mild reaction conditions, yielding homochiral (or racemic) cyclopentane derivativel.

Enantiospecific synthesis of substituted bicyclo[2.1.1]hexane-1-carboxylic acids and esters

Abstract The base promoted ring contraction of the readily accessible homochiral 2-oxo-1-norbornyl inflates 3 in 60% ethanol takes place with formation of bicyclo[2.1.1]hexane ( 4a ), ( + )- or (−)-7,7-dimethyl-bicyclo[2.1.1]hexan-1-carboxylic acids ( 4c or 4b ) and the corresponding ethyl esters in good yields.

Enantiospecific synthesis of 3-substituted alkylidinecyclopentanes

Abstract The solvolysis of (−)-(1R)-2,2-dimethyl-3-oxotrifluoromethylsulfonyloxynorbornane [(−)-8] in 60% ethanol takes place with cleavage of C-2/C-3 bond to afford a mixture of (−)-(IR)-3-(1-methylethylidene)cyclopentane car☐ylic acid (−)-( 1c ) (56%) and its corresponding ethyl ester (−)- 1d (21%).

Density functional theory study of self-association of N-methylformamide and its effect on intramolecular and intermolecular geometrical parameters and the cis/trans population

The single-point total energy (E) of several acyclic and cyclic oligomers of N-methylformamide (NMF) was computed by the first time without any geometrical restriction, using the B3LYP6-31G* method of the density functional theory in order to determine the effect of self-association on intramolecular geometrical parameters of cis- and trans-NMF, the intermolecular distances of the hydrogen-bonding chains formed by NMF as well as intermolecular association energies including counterpoise corrections. It is concluded that liquid NMF exists mainly as polymers formed by self-association of trans-NMF units, whereas the cis-NMF isomer occurs as isolated units inserted along the chains. These computational results are in accordance with the experimentally determined predominance (ca. 90%) of trans-NMF population by means of (1)H- NMR and other spectroscopic techniques, but in severe contradiction with a recent interpretation of x-ray diffraction data on liquid NMF, postulating a cyclic trimer of cis-NMF (c-C(3)) as the predominating species. The counterpoise-corrected values of the association energy, DeltaE(CP), calculated for cyclic oligomers, increase with the polymerization degree (n) revealing a high grade of cooperative effect for amidic hydrogen-bonded chains. Noteworthy, the difference between the DeltaE(CP) values of the cyclic cis- and trans-homooligomers of NMF is positive for n=2 and 3 but negative for n > or =4.

A facile synthesis of homochiral 1-norbornanecarboxylic acids and 1-norbornanecarbonitriles

Abstract A general method for the preparation of the title compounds from naturally occurring homochiral 2-norbornanones is presented. The key step is the Tf 2 O induced Wagner-Meerwein rearrangement of the corresponding cyanohydrins.

Synthesis of methyl (1R,2S)-α,α-dimethyl-3-oxo-2-pentylcyclopentaneacetate. A model procedure for the preparation of chiral jasmonoids and prostaglandins

Abstract An expeditious procedure for the enantiospecific preparation of the trans -2,3-disubstituted cyclopentanone moiety starting from natural 2-norbornanones is described. New reaction conditions for the reaction of sterically hindered ketones with triflic anhydride, as well as for the Sue5f8O cleavage of bridgehead triflates have been developed.