Producción Científica Profesorado

Synthesis of New Chiral Derivatives of N,N?-Dimethylpropyleneurea (DMPU) and Examination of Their Influence on the Regio- and Enantioselectivity of Addition of 2-(1,3-Dithianyl)lithium to Cyclohex-2-en-1-one



Lopez Ruíz, Heraclio

2002

E. Juaristi, M. Hernandez-Rodriguez, Heraclio López-Ruiz, J. Aviña, O. Muños-Muniz, M. Hayakawa, D. Seebach. Synthesis of New Chiral Derivatives of N,N-Dimethylpropyleneurea (DMPU) and Examination of Their Influence of the Regio- and Enentioselective of Addition of 2(1,3Dithianyl)lithium to Cyclohex-2-en-one. Helvetica Chimica Acta, 85, 1999-2007 (2002). DOI: 10.1002/1522-2675(200207)85:7<1999::AID-HLCA1999>3.0.CO;2-K


Abstract


The preparation of three new chiral derivatives of DMPU (N,N?-dimethylpropyleneurea) is described (Schemes?24); one type of derivative carries 1-phenylethyl or 1-cyclohexylethyl groups at the N-atoms of the tetrahydropyrimidin-2(1H)-one ring (2 and 4), another type of derivative is substituted at C(4) and C(6) of the heterocyclic ring (7). The potential of these chiral Lewis bases as promoters in the regio- and/or enantioselective addition of 2-(1,3-dithianyl)lithium to cyclohex-2-en-1-one was explored; they are all unable to effect enantioselective addition; the derivatives with branched substituents at the N-atoms do not shift the addition mode from 1,2 to 1,4, while the 3,4,5,6-tetrahydro-1,3,4,6-tetramethylpyrimidin-2(1H)-one does (Scheme?5). The results provide useful information regarding the nature of the nucleophilic organolithium reagent: obviously, the steric hindrance to Li complexation on the CO O-atom of the tetrahydropyrimidin-2(1H)-one by branched substituents at N-atoms (cf. X-ray crystal structure of 2 in the Fig.) prevents solvent-separated-ion-pair (SSIP) formation; this was confirmed by PM3 and B3LYP/3-21-G(d)//PM3 calculations (Scheme?6).



Producto de Investigación




Artículos relacionados

Synthesis and Structures of some Lithium and Sodium (Aminoalcoholato)hydrido Aluminates

Aroylthioureas: new organic ionophores for heavy-metal ion selective electrodes

Phenylboronic acid catalyzed-cyanide promoted, one-pot synthesis of 2-(2-hydroxyphenyl)benzoxazole d...

Diastereoselective alkylation of chiral glycinate derivatives containing the ?-phenylethyl group.

Diastereoselective alkylation of chiral glycinate derivatives containing the ?-phenylethyl group.

Addition reaction of benzylbenzylidenenamine to lithium enolates of 1,3-dioxolan-4-one: synthesis of...

Et3, and efficient Mediator for Xanthate Transfer Based Radical Processes.

Preparation of N-aryl-substituted spiro-?-lactams via Staudinger cycloaddition

Phenylmethyl 2,3,4-tri-O-acetyl--D-fucopyranoside

A practical access to acyl radicals from acyl hydrazides