Fluorine containing amino acids and their derivatives. 7. Synthesis and antitumor activity of α- and γ-substituted methotrexate analogs

Reduction of Metal-Stabilized α-CF3-Carbenium Ion Complexes under Mild Conditions: Synthesis, Structures, and Reactivity

“…[18] Table 4). These results Treatment of the propargyl alcohol complexes [{Co 2 (CO) 6 }{µ-η 2 ,η 2 -RCϵCC(OH)(CF 3 )H}] (1؊2) by are in accord with those reported by Mayr et al, [13] which show that the carbenium ion complex HBF 4 · Et 2 O in ether did not afford any precipitate, as expected for the formation of the related carbenium ion salts. [{Co 2 (CO) 5 P(C 6 H 5 ) 3 }{µ-η 2 ,η 3 -HCϵCCH(C 6 H 5 )}] ϩ is less electrophilic than the parent carbenium ion [Co 2 (CO) 6 {µ-In contrast, the complexed alcohols 3؊7 gave, under the same experimental conditions, the corresponding carben-η 2 ,η 3 -HCϵCCH(C 6 H 5 )}] ϩ .…”

“…On the other hand, if the carbenium ion complex is strongly anion proceed through a radical pathway, whereby the tranWe would also like to outline that by either using the sient radical pair species can either recombine in the solvent THF/CH 2 Cl 2 system or by the action of Zn/CH 2 Cl 2 , our α-cage to give coupling reaction [21] as illustrated by formation CF 3 -propargyl alcohol complexes [{Co 2 (CO) 4 L 2 }{µ-η 2 ,η 2 -of 18a, b or, after diffusion from the solvent cage, would RCϵCC(OH)(CF 3 )H}] (3؊7) gave exclusively the reabstract a hydrogen atom from the solvent to afford the duction products, and never the coupling reaction products, reduced alkyne adduct 13 (Scheme 8). which is the major product observed with [{Co 2 (CO) 6 }{HCϵCCH(C 6 H 5 )(OH)}] (Scheme 6).…”

“…, along with the alkyne-thioether diastereomers Co 2 (CO) 5 P(C 6 H 5 ) 3 , R = CH 3 (CH 2 ) 4 -(3a,b), R = C 6 H 5 -(4a,b); M 2 L 6 = Co 2 (CO) 4 dppm, R = C 6 H 5 -(5); M 2 L 6 = Co(CO) 3 {Co(CO) 3 MoCp(CO) 2 }{µ-η 2 ,η 2 -CH 3 (CH 2 ) 4 CϵCCH(CF 3 )(SMe)}] (18a,b). Presumably, all the reduction reactions proceed MoCp(CO) 2 , R = CH 3 (CH 2 ) 4 -(6a,b), R = C 6 H 5 -(7a,b).…”

“…The capacity of these ions to be reduced, either directly from the complexed propargyl alcohols or starting from the related metal-stabilized carbenium ions, has also been investigated. [12] obtained also as two diastereomers 6a, b and 7a, Substitution of a carbonyl ligand of complexes 1؊2 by either a monophosphane [P(C 6 H 5 ) 3 ] or a chelating phos-b, respectively. The complexed alcohols 1؊7 thus obtained have the α-CF 3 substituent on the carbon atom bearing the phane such as dppm ϭ [{P(C 6 H 5 ) 2 } 2 CH 2 ] using standard methods [10] leads to the phosphaneϪ[Co 2 ]-complexed al-hydroxyl function, while the C-4 acetylenic carbon is either substituted by an alkyl or an aryl substituent.…”

Stereospecific substitution at α‐carbon to trifluoromethyl group: Application to optically active fluorinated amino acid syntheses

“…46 We made a preliminarily study of the halogenations of 3-isopropyloxy-1,1,1-trifluoro-2-propanol 3a to 8 with a series of reagents (Scheme 3). Our trials, as well as previous reports, found that only PPh 3 /CCl 4 was effective.…”