Synthesis of a muscarinic receptor antagonist via a diastereoselective Michael reaction, selective deoxyfluorination and aromatic metal-halogen exchange reaction

An efficient synthesis of a structurally unique, novel M(3) antagonist 1 is described. Compound 1 is conveniently disconnected retrosynthetically at the amide bond to reveal the acid portion 2 and the amine fragment 3. The synthesis of key intermediate 2 is highlighted by a ZnCl(2)-MAEP complex 19 catalyzed diastereoselective Michael reaction of dioxolane 7 with 2-cyclopenten-1-one (5) to establish the contiguous quaternary-tertiary chiral centers and a subsequent geminal difluorination of ketone 17 using Deoxofluor in the presence of catalytic BF(3).OEt(2). The synthesis of the amine moiety 3 is highlighted by the discovery of a novel n-Bu(3)MgLi magnesium-halogen exchange reaction for selective functionalization of 2,6-dibromopyridine. This new and practical metalation protocol obviated cryogenic conditions and upon quenching with DMF gave 6-bromo-2-formylpyridine (26) in excellent yield. Further transformations afforded the amine fragment 3 via reductive amination with 35, Pd-catalyzed aromatic amination, and deprotection. Finally, the highly convergent synthesis of 1 was accomplished by coupling of the two fragments. This synthesis has been used to prepare multi-kilogram quantities of the bulk drug.     

A general palladium-catalyzed coupling of aryl bromides/triflates and thiols

We have developed an efficient palladium-catalyzed carbon-sulfur bond formation reaction of aryl bromides, triflates, and activated aryl chloride. Using this protocol, we have shown tolerance to a wide variety of aryl thiols and alkyl thiols that can also be used as sulfide equivalents. [reaction: see text]     

Synthesis,Structures, and Some Reactions of [(Thioacyl)thio]‐ and (Acylseleno)antimony and ‐bismuth Derivatives ((RCSS)xMR$\rm{_{{\bf 3 - }{\bf x}}^{\bf 1} }$ and (RCOSe)xMR$\rm{_{{\bf 3 - }{\bf x}}^{\bf 1} }$ with M = Sb,Bi and x = 1–3)

A series of [(thioacyl)thio]‐ and (acylseleno)antimony and [(thioacyl)thio]‐ and (acylseleno)bismuth, i.e., (RCSS)_xMR and (RCOSe)_xMR (M = Sb, Bi, R¹ = aryl, x = 1–3), were synthesized in moderate to good yields by treating piperidinium or sodium carbodithioates and ‐selenoates with antimony and bismuth halides. Crystal structures of (4‐MeC₆H₄CSS)₂Sb(4‐MeC₆H₄) ( 9b′ ), (4‐MeOC₆H₄COSe)₂Sb(4‐MeC₆H₄) ( 12c′ ), (4‐MeOC₆H₄COS)₂Bi(4‐MeC₆H₄) ( 15c′ ), and (4‐MeOC₆H₄CSS)₂BiPh ( 18c ) along with (4‐MeC₆H₄COS)₂SbPh ( 6b ) and (4‐MeC₆H₄COS)₃Sb ( 7b ) were determined (Figs. 1 and 2). These compounds have a distorted square pyramidal structure, where the aryl or carbothioato (= acylthio) ligand at the central Sb‐ or Bi‐atom is perpendicular to the plane that includes the two carbodithioato (= (thioacyl)thio), carboselenato (= acylseleno), or carbothioato ligand and exist as an enantiomorph pair. Despite the large atomic radii, the C?S ??? Sb distances in (RCSS)₂MR¹ (M = As, Sb, Bi; R¹ = aryl) and the C?O ??? Sb distances in (RCOS)_xMR (M = As, Sb, Bi; x = 2, 3) are comparable to or shorter than those of the corresponding arsenic derivatives (Tables 2 and 3). A molecular‐orbital calculation performed on the model compounds (MeC(E)E¹)_3?xMMe_x (M = As, Sb, Bi; E = O, S; E¹ = S, Se; x = 1, 2) at the RHF/LANL2DZ level supported this shortening of C?E ??? Sb distances (Table 4). Natural‐bond‐orbital (NBO) analyses of the model compounds also revealed that two types of orbital interactions n_S → σ and n_S → σ play a role in the (thioacyl)thio derivatives (MeCSS)_3?xMMe_x (x = 1, 2) (Table 5). In the acylthio‐MeCOSMMe₂ (M = As, Sb, Bi), n_O → σ contributes predominantly to the orbital interactions, but in MeCOSeSbMe₂, none of n_O → σ and n_O → σ contributes to the orbital interactions. The n_S → σ and n_S → σ orbital interactions in the (thioacyl)thio derivatives are greater than those of n_O → σ and n_O → σ in the acylthio and acylseleno derivatives (MeCOE)_3?xMMe_x (E = S, Se; M = As, Sb, Bi; x = 1, 2). ?The reactions of RCOSeSbPh₂ (R = 4‐MeC₆H₄) with piperidine led to the formation of piperidinium diphenylselenoxoantimonate(1?) (= piperidinium diphenylstibinoselenoite) (H₂NC₅H₁₀)⁺Ph₂SbSe^?, along with the corresponding N‐acylpiperidine (Table 6). Similar reactions of the bis‐derivatives (RCOSe)₂SbR¹ (R, R¹ = 4‐MeC₆H₄) with piperidine gave the novel di(piperidinium) phenyldiselenoxoantimonate(2?) (= di(piperidinium) phenylstibonodiselenoite), [(H₂NC₅H₁₀)⁺]₂(PhSbSe₂)^2?, in which the negative charges are delocalized on the SbSe₂ moiety (Table 6). Treatment of RCOSeSbR (R, R¹ = 4‐MeC₆H₄) with N‐halosuccinimides indicated the formation of Se‐(halocyclohexyl) arenecarboselenoates (Table 8). Pyrolysis of bis(acylseleno)arylbismuth at 150° gave Se‐aryl carboselenoates in moderate to good yields (Table 9).     

Formation of CN(B2Σ+) by electron-impact dissociation of BrCN

Electron impact (8.4–20 eV) on BrCN resulted in the formation of polarized CN(B–X) emission, from which the polarization and the vibrational distribution of the CN(B) fragment were obtained as a function of impact energy. The data indicate that the dissociation process proceeds mainly via the states having ^I Σ⁺(0⁺) and/or ¹A′ symmetry in the energy range observed.     

Sulfur-containing polymers. XVIII. Preparation and properties of thiuram polysulfide polymers

Thiuram polysulfide polymers have been prepared from alkali metal bisdithiocarbamates either by oxidation with ammonium persulfate or by polycondensation with sulfur chlorides. In some cases, isothiocyanate formation and/or thiourea formation were noticed. The polymer properties were significantly affected by the diamines used. Polymers derived from p-phenylenediamine decomposed gradually at room temperature with the liberation of elemental sulfur. Polymers based on aliphatic primary diamines were more stable. Piperazine gave the most stable polymer.     

Sulfur-containing polymers. VII. Alternating copolydisulfides

A variety of copolydisulfides have been synthesized in high yields by the fragmentation polymerization of bis(sulfenyl thiocarbonates) with dithiols in the presence of triethylamine. The structures of the copolymers were investigated by x-ray and NMR studies. Alkylene–arylene copolydisulfides were alternating. Alkylene–arylene copolymers derived from arylene dithiols were alternating, and those prepared from alkylene dithiols were generally random. It was concluded that the present procedure makes it possible to prepare various kinds of alternating copolydisulfides by using appropriate combinations of a bis(sulfenyl thiocarbonate) and a dithiol.