214477-57-3Relevant academic research and scientific papers
Asymmetric synthesis of 4-formyl-1-(ω-haloalkyl)-β-lactams and their transformation to functionalized piperazines and 1,4-diazepanes
Dekeukeleire, Stijn,D'Hooghe, Matthias,Vanwalleghem, Matthieu,Van Brabandt, Willem,De Kimpe, Norbert
, p. 10827 - 10834 (2013/01/15)
Chiral piperazine and 1,4-diazepane annulated β-lactams, prepared from the corresponding (3R,4S)-4-imidoyl-1-(ω-haloalkyl)azetidin-2-ones through reduction with sodium borohydride in ethanol, were transformed into novel methyl (R)-alkoxy-[(S)-piperazin-2-yl]acetates and methyl (R)-alkoxy-[(S)-1,4-diazepan-2-yl]acetates upon treatment with hydrogen chloride in methanol. On the other hand, bromination of (3R,4R)-1-allyl-4-formyl-β- lactams and (3R,4S)-1-allyl-4-imidoyl-β-lactams in dichloromethane, followed by sodium borohydride reduction of the resulting dibrominated azetidin-2-ones in ethanol, did not afford the envisaged bicyclic β-lactams but unexpectedly furnished (3R,4S)-1-(2-bromo-2-propenyl)azetidin-2-ones instead.
Stereoselective allylation of 4-oxoazetidine-2-carbaldehydes. Application to the stereocontrolled synthesis of fused tricyclic β-lactams via intramolecular Diels-Alder reaction of 2-azetidinone-tethered trienes
Alcaide, Benito,Almendros, Pedro,Salgado, Nati R.
, p. 3310 - 3321 (2007/10/03)
Allylation reactions of racemic and optically pure 4-oxoazetidine-2- carbaldehydes were investigated both under anhydrous conditions and in aqueous media. Different Lewis acid or metal mediators showed varied diastereoselectivities on product formation du
Rapid entry to enantiopure polycyclic β-lactams via intramolecular nitrone-alkene cycloaddition of 2-azetidinone-tethered alkenylaldehydes
Alcaide, Benito,Alonso, Jose M.,Aly, Moustafa F.,Saez, Elena,Martinez-Alcazar, M. Paz,Hernandez-Cano, Felix
, p. 5391 - 5394 (2007/10/03)
New enantiomerically pure fused 2 or bridged 3 polycyclic β-lactam systems are regio- and stereoselectively prepared via intramolecular nitrone- alkene cycloaddition of 2-azetidinone-tethered alkenyl-aldehydes 1. The regioselectivity of the cycloaddition
Alkyne-Co2(CO)6 complexes in the synthesis of fused tricyclic β- lactam and azetidine systems
Alcaide, Benito,Polanco, Concepcion,Sierra, Miguel A.
, p. 6786 - 6796 (2007/10/03)
A synthetic approach to racemic and enantiomerically pure, fused tricyclic 2-azetidinones and azetidines has been developed by using a Pauson- Khand (P-K) reaction on monocyclic enyne-β-lactams as the key synthetic step. The access to cyclization precursors, monocyclic β-lactams 1-7, was achieved by Staudinger reaction of enyne imines 8 and 9 and D-glyceraldehyde imines 10 and (benzyloxy)- or phenoxyacetyl chlorides. Enyne imines 8 and 9 formed cis-2-azetidinones 1 and 2 having the required enyne moiety. cis-2- Azetidinones 11 were obtained as single diastereomers and transformed to enyne-2-azetidinones 3 and 5 by standard methodology. Alternatively, 4- formyl-2-azetidinones 14 were prepared by cyclization of p-anisyl glyoxal diimine and (benzyloxy)acetyl chloride and converted to racemic enyne-β- lactams 4 and 6 by standard reactions. Enyne-2-azetidinones 1-7 were reacted with Co2(Co)8 to quantitatively yield the corresponding alkyne-Co2(CO)6 complexes. Reaction of such complexes with different promoters, especially heat and TMANO, formed tricyclic 2-azetidinones 15-19 with the ring system fused to the C3-C4 and C4-N1 lactam bonds. Yields were usually high, and the processes were highly diastereoselective. The exceptions were enyne-2- azetidinones 2 and 3a bearing N-propargyl moieties. These products decomposed to mixtures of unidentifiable products. Inhibition of the amide resonance was postulated as responsible for the failure of β-lactams 2 and 3a to form tricyclic systems. In fact, the analogous enyne-azetidines 20a,b smoothly cyclized to form the corresponding tricyclic systems. This approach to tricyclic azetidines was extended to prepare different products. A new, unprecedented, N1-C2 bond breakage was also observed in the azetidine ring. The results described show that the P-K reaction is a suitable approach to tricyclic 2-azetidinones and azetidines. These are the first examples reported for a P-K reaction in with the enyne system is tethered to a strained heterocyclic four-membered ring.
