Joel L. Terán

The Stabilizing Role of the Intramolecular C-H···O Hydrogen Bond in Cyclic Amides Derived From α-Methylbenzylamine.

A series of five-, six-, seven-, and eight-membered lactams containing the chiral auxiliary α-methylbenzylamine were structurally analyzed and further studied by DFT calculations with the purpose to examine with detail the previously detected intramolecular C-H···O hydrogen-bonding interaction formed between the hydrogen atom of the α-methylbenzylamine and the carbonyl group of the cyclic amide. The main objective was to establish whether its presence does have a tangible relevance in their spatial arrangement in solution and in the solid state or is a simple and not stabilizing interaction.

Oxidation of chiral non-racemic pyridinium salts to enantiopure 2-pyridone and 3-alkyl-2-pyridones

Abstract Oxidation of chiral non-racemic pyridinium salt 1a and 3-alkyl pyridinium salts 1b and 1c with potassium ferricyanide in an alkaline medium provides a short and practical access to enantiomerically pure 2-pyridone ( 2a ) and 3-alkyl-2-pyridones ( 2b and 2c ) in high yields and very good regioselectivity from derivatives 1 ( b – c ).

New methodology for the synthesis of enantiopure (3R,2aR)-(−)-3-phenyl-hexahydro-oxazolo[3,2-a]-pyridin-5-one: a synthesis of (S)-(+)-coniine

Abstract A new and efficient methodology for the enantiopure synthesis of (3R,2aR)-(−)-3-phenyl-hexahydro-oxazolo[3,2-a]pyridin-5-one 3 starting from (1′R)-(−)-1-(2′-hydroxy-1′-phenyl-ethyl)-(1H)-pyridin-2-one 1 is described. In addition, the enantiospecific synthesis of (S)-(+)-coniine hydrochloride 6 in good yield from 3 is reported.

A SHORT SYNTHESIS OF INDOLIZIDINE (+)-209B FROM (3R,6S,8aS)-(-)-6-METHYL-3-PHENYLHEXAHYDROOXAZOLO[3,2-a]-PYRIDIN-5-ONE

The synthetic potential of enantiopure (3R,6S,8aS)-(-)-6-methyl-3-phenylhexahydrooxazolo[3,2-a]pyridin-5-one 2 is illustrated by a short synthesis of the 5,8-disubstituted indolizidine alkaloid (+)-209B.

Unexpected retro-Michael reaction of (−)-(1′S,4aS,8aR)- and (+)-(1′S,4aR,8aS)-4a-ethyl-1-(1-phenylethyl)octahydroquinolin-7-ones

Abstract An unexpected retro-Michael reaction of (−)-(1′ S ,4a S ,8a R )-and (+)-(1′ S ,4a R ,8a S )-4a-ethyl-1-(1′-phenylethyl)octahydroquinolin-7-ones 1 and 2 is described. In addition, a diastereospecific intramolecular Michael reaction of 3 ·HCl and 4 ·HCl is reported.

Reactivity of (1′ S )-1-(1′-phenyl-ethyl)-4-hydroxy-piperidin-2-one with Lawesson's reagent

The study of the reactivity of diasteromeric mixture (1′S)-1-(1′-phenyl-ethyl)-4-hydroxy-piperidine-2-one 2 with the Lawessons reagent in different conditions is described.

Diastereoselective Approach to cis-4-Methyl/thiol-Pipecolic Esters Based on RCM Reaction and Conjugate Michael Addition

Abstract A synthetic route for the access to enantiopure cis-4-methyl/thiol-pipecolic esters is presented. It is based on the ring-closing metathesis reaction to build the α,β-unsaturated piperidin-2-one derived from (S)-(–)-phenylethylamine, followed by either diastereoselective conjugate addition of methylorganocuprate allowing access to cis-4-methyl pipecolic ester or by tandem diastereoselective hydrosulforization–thionization reaction providing access to cis-4-thiol pipecolic ethyl esters. GRAPHICAL ABSTRACT

2,2-Dimethyl-5-(2-nitro­benzyl­idene)-1,3-dioxane-4,6-dione

The asymmetric unit of the title compound, C13H11NO6, contains two molecules in both of which the six-membered 1,3-dioxane-4,6-dione ring shows a screw-boat conformation. The dihedral angles between the best planes through the six-membered rings are 47.8 (2) and 49.8 (2)°. In the crystal, C—H⋯O interactions link the molecules, building a supramolecular sheet parallel to the c axis.

Regioselective Endocyclic Oxidation of Enantiopure 3‐Alkylpiperidines: Synthesis of (3S,5S)‐(‐)‐3‐Ethyl‐5‐Methylpiperidine

Abstract An efficient regioselective endocyclic oxidation of enantiopure 3‐alkylpiperidines 1(a–c) with bromine in acetic acid to generate the corresponding 5‐alkylpiperidin‐2‐ones 3(a–c) as main product is described. In addition, starting from 3a or 3b, the synthesis of (3S,5S)‐(‐)‐3‐ethyl‐5‐methylpiperidine 6 · HCl was achieved. Finally, the X‐ray single‐crystal analysis of compound 4 is reported.

Crystal structures of two chiral piperidine derivatives: 1-[(1R)-2-hy-droxy-1-phenyl-eth-yl]piperidin-4-one and 8-[(1S)-1-phenyl-eth-yl]-1,4-dioxa-8-aza-spiro-[4.5]decane-7-thione.

The conformation of the piperidine ring is modified by the hybridization state of the C atom in the α-position to the piperidinic N atom.