Synthesis of 5,6-dihydro-4H-1,3-oxazines from neutral and cationic platinum(II) nitrile complexes. X-ray structure of trans-[Pt(CF3){H2CH2}(PPh3)2]BF4

Stereoselective [2 + 3] cycloaddition of nitrones to platinum-bound organonitriles. First enantioselective synthesis of Δ4-1,2,4-oxadiazolines†

“…The identity of the products was confirmed by elemental analysis, FAB mass spectrometry, IR and 1 H, 13 C{ 1 H} and 195 Pt NMR spectroscopy. In the IR spectra, disappearance of the C᎐ ᎐ ᎐ N vibration at 2292 cm Ϫ1 was accompanied by the appearance of a new intense band for the C᎐ ᎐ N stretching in a range 1630-1638 cm Ϫ1 which is in good agreement with the values found for the previously described [PtCl 2 (oxadiazoline) 2 ] complexes (1622-1660 cm Ϫ1 ).…”

“…General features of the major product are the same as described above for the sterically less demanding nitrones and therefore we assign the cis-geometry to this isomer. The minor isomer, which is also visible by TLC as a separate spot with a higher R f value, shows 1 H and 13 C signals typical for the oxadiazoline ligand but exhibits only one signal for the two methyl groups of the dmso ligand (3.47 ppm in 1 H, 44.4 ppm in 13 C). As irradiation into this singlet does not generate any NOE with other signals, we attribute transgeometry to this isomer.…”

“…1 In this context, activation of nitriles towards nucleophilic attack received much attention 2 and especially platinum complexes proved to be useful substrates for this kind of transformation involving a wide variety of nucleophiles such as oximes, 3 hydroxylamines, 4 alcoholates, 5 hydroxide, 6 ammonia, 7 amines, 8 carbanions, 9 phosphorous ylides, 10 or thiols. 11 In spite of the high potential of this method, the enhanced reactivity of platinum-coordinated nitriles was only rarely used for cyclization reactions, and only some examples of the addition of chloroalkoxides to give coordinated oxazolines 12 or 1,3oxazines, 13 or the reaction with aziridines to form coordinated amidines which, upon release from the metal center, cyclize to give the corresponding imidazolines, are found in the literature. 14 In the course of our recent studies on the synthesis of heterocycles via metal-mediated reactions of coordinated nitriles, we concentrated on the [2 ϩ 3] cycloaddition of nitrones to nitriles.…”

Some 60 new space-group corrections

“…(29) TAZPAD: 1,3,5-triaza-7-phospha-adamantane (monophospha-urotropine), C 6 H 12 N 3 P (Fluck et al, 1977) This structure was reported in the chiral space group R3 [hexagonal axes 9.618 (3), 7.004 (3) A Ê ; Z = 3, not`1' as printed). It is properly described in achiral R3m and is isostructural with AZPADO and AZPADS, which were originally described in Cm (Jogun et al, 1978; (Michelin et al, 1994) This compound was reported in space group P " 3 (No. 147) with a = 22.590 (4), c = 15.970 (3) A Ê , Z = 6.…”

Chemistry and Biological Activity of Platinum Amidine Complexes

“…Of particular synthetic relevance is the preparation of oxazolines by preliminary reaction of trans-[PtCl 4 (NCEt) 2 ] with amino alcohols H 2 NCRR 1 CR 2 R 3 OH having varying degrees of substitution at the methylene groups, which fosters selective nucleophilic attack by the ÀNH 2 moiety, subsequent liberation of the hydroxo-functionalized amidines by reaction with dppe, and final conversion of the amidine to the oxazoline promoted by zinc(II) chloride according to Scheme 12. [84] Interestingly, the conversion of Pt II -coordinated nitriles to oxazolines [85] and oxazines [86] was previously reported to occur through addition of ClCH 2 CH 2 O À and ClCH 2 CH 2 CH 2 O À , respectively, to coordinated nitriles in cis-and trans-[PtCl 2 -…”