A polycyclic imidazolophosphinine
has been synthesized by collapse
of the bridge of an appropriate 7-phosphanorbornene. This stable compound
has been characterized by X-ray crystal structure analysis. It is
fully planar with a PC bond length of 1.733(4) Å. The
lone pair at P is poorly reactive and corresponds to HOMO–3.
The compound reacts with a protic acid and methyl iodide at the sp2 nitrogen and with AuCl with the α-methoxy substituent,
yielding a zwitterionicacylphosphidewhose complexation at P gives
a bis-gold complex. Both the protonated product and the bis-gold complex
have been characterized by X-ray crystal structure analysis.
Here, we report a visible-light enabled platform for the photochemical reduction of 1,2-dicarbonyl compounds to α-hydroxy carbonyl derivatives which utilizes diisopropylethylamine (Hünig’s base) as a reductant. This reaction tolerates a...
An unprecedented palladium-catalyzed intramolecular Ullmann-type
cyclization of carbonyl-stabilized phosphonium ylides with aryl bromides
was successfully developed. Furthermore, a base-promoted chemoselective
hydrolysis of exocyclic P–C bond of the corresponding phosphonium
salts delivered various phosphachromones. Excellent selectivity and
high efficiency and good functional group tolerance were observed.
The first total synthesis of 5′-O-α-d-glucopyranosyl tubercidin was successfully developed. It is a structurally unique disaccharide 7-deazapurine nucleoside exhibiting fungicidal activity, and was isolated from blue-green algae. The total synthesis was accomplished in eight steps with 27% overall yield from commercially available 1-O-acetyl-2,3,5-tri-O-benzoyl-β-d-ribose. The key step involves stereoselective α-O-glycosylation of the corresponding 7-bromo-6-chloro-2′,3′-O-isopropylidene-β-d-tubercidin with 2,3,4,6-tetra-O-benzyl-glucopyranosyl trichloroacetimidate. All spectra are in accordance with the reported data for natural 5′-O-α-d-glucopyranosyl tubercidin. Meanwhile, 5′-O-β-d-glucopyranosyl tubercidin was also prepared using the same strategy.
The unprecedented 2,2'-bis(azaphosphindole) has been synthesized via a new route. Reaction with NaH afforded a dianion derivative 5, which is easily transformed to alkylated bis(azaphosphindole) or (Z)-P,P,N,N-cisoid diazadiphosphafulvalene. The reaction features good regioselectivity and high steroselectivity. Relatively strong fluorescence is observed with diazadiphosphafulvalenes. The X-ray crystal structure analysis showed that dianion ligand 5 is bonded to two Na atoms in a bridging cis-fashion, which allows the synthesis of diazadiphosphafulvalene in a highly stereoselective approach.
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