N-Heteropolycyclic Compounds from the Formal Intramolecular (4 + 1)-Cycloaddition of Chromium Aminocarbenes

Abstract

Chromium aminocarbenes tethered to dienes of all three electronic natures undergo an efficient intramolecular (4 + 1)-cycloaddition to give N-heteropolycyclic compounds. Ligands on chromium had a profound effect on the course of the reaction.

Synthesis and Structural Analysis of Palladium(II) Complexes Containing Neutral or Anionic C2-Symmetric Bis(oxazoline) Ligands: Effects of Substituents in the 5-Position

“…First, optically active amino alcohols, ( R )-1-amino-2-methyl-1-phenylpropan-2-ol ( 6a ) and ( R )-2-amino-1,1,2-triphenylethanol ( 6c ), were prepared using modifications of reported procedures (Scheme 1). 67,68 The reaction of chiral amino alcohol 6a with oxalyl chloride in the presence of triethylamine afforded N 1 , N 3 -bis(( R )-2-hydroxy-2-methyl-1-phenylpropyl)-2,2-dimethylmalonamide ( 7a ); then, intramolecular dehydration condensation of 7a using Ti(O i Pr) 4 as a catalyst afforded 2,2′-(2-propylidene)bis{(4 R )-4-phenyl-5,5-dimethyl-2-oxazoline} ( 1a ). One-pot syntheses were conducted for 2,2′-methylenebis{(4 R )-4-phenyl-5,5-dimethyl-2-oxazoline} ( 1b ) and 2,2′-methylenebis{(4 R )-4,5,5-triphenyl-2-oxazoline} ( 1c ).…”

Carbon Dioxide-Mediated C(sp2)–H Arylation of Primary and Secondary Benzylamines

“…The reaction mixture was extracted with CH 2 Cl 2 (2 × 10 mL), dried over Na 2 SO 4 , and concentrated in vacuo to give the crude product as a colorless oil, which was subjected to column chromatography on silica gel using CH 2 Cl 2 /MeOH (96:4) to give product as a colorless oil (0.52 g, 32%), which was found to match with literature data. 12…”

Formal [4+1] Annulation Reactions in the Synthesis of Carbocyclic and Heterocyclic Systems

“…The reaction was rationalized to proceed via a metal-Diels–Alder reaction of the CrC dienophile and a reductive elimination of the chromium moiety. An intramolecular variant of this formal [4+1] annulation of the chromium aminocarbenes was also achieved by Spino’s group to obtain an efficient entry to a variety of bicyclic N -heterocyclic compounds with acceptable yields, which are commonly detected in many natural alkaloids …”