RING-CHAIN HALOGENOTROPIC TAUTOMERISM. 2,2-DIPHENYL-1,2ι⁴-THIAPHOSPHOLANIUM BROMIDE ⇋ 3-BROMOPROPYLDIPHENYLPHOSPHINE SULFIDE

Bisphosphine‐Functionalized Cyclic Decapeptides Based on the Natural Product Gramicidin S: A Potential Scaffold for Transition‐Metal Coordination

“…Their molecular structures ( Figure 2, Table 1) show pseudo squareplanar coordination of nickel by three nitrogen atoms and one oxygen atom, like that for the non-functionalized template 4. [14] The bond lengths and angles around nickel are very similar for 8 b and the two independent molecules for 8 c. A notable difference is the manner in which the Nbenzyl and alkylphosphinyl groups are rotated, which may be due to packing effects in the solid state. Importantly, the desired and expected S configuration at the a-carbon atom of the embedded glycine fragment is confirmed for both 8 b and 8 c. Ni(1)ÀN(1) 1.946 (7), Ni(1)ÀN(8) 1.847 (7), Ni(1)ÀN(22) 1.859 (7), Ni(1)À O(26) 1.865 (6) (3), O(26)-Ni(1)-N(1) 90.5 (3).…”

“…Attempts to extend the alkylation with the next higher homologue (n = 3), the propyl-containing 12 a or its bromo derivative 12 b, was unsuccessful, probably due to self alkylation of the substrate under the reaction conditions. [14] Stereochemistry of amino acids: Products 8 a-c were each obtained as single diastereomers, whereas the phosphanation and alkylation of the anion of chiral 4 might have given two. The high selectivity is evident from the single, sharp 31 P NMR resonance (8 a 49.3; 8 b 36.7; 8 c 42.3 ppm) ob-served in the crude reaction mixtures.…”

“…TFA (linear gradient of 50 %!80 % B). Compounds 4, [22,11] and 12 b [14] were synthesized according to literature procedures. (10): [23a] nBuLi (0.63 mL of a 1.6 m solution in n-hexane; 1.0 mmol) was added slowly to a solution of Ph 2 PH (0.19 g, 1.0 mmol) in dry THF (15 mL) at À78 8C, after which the solution turned orange.…”

“…Data for 1: [4] Yield: 0.38 g (72 %); 31 8 H;CH),2 H;CH),8 H;CH),2 H;CH),5.60 (d,3 + , 542 (62) [M+H] + , 496 (9) [MÀCO 2 ] + , 363 (14) [MÀC 14 H 11 Synthesis of 7 b: Compound 7 b was synthesized according to literature procedures [4d] in 61 % yield. 31 6 H;CH),6 H;CH),2 H Synthesis of 3: LiOH (10 mL of a 0.2 m solution in H 2 O) was added dropwise to a solution of 7 b (1.0 mmol, 0.50 g) in THF (3 mL) at 0 8C, and the resulting mixture was stirred for 2 h. Neutralization with conc.…”

Intramolecular cyclization of ω‐haloalkylsubstituted thiophosphorylacetonitriles: Synthesis and stereochemistry of 3‐cyano‐2‐oxo‐1,2‐thiaphosphacyclanes

“…Moreover, despite the fact that 1,2-thiaphosphacyclanes should be of no less practical interest, at the beginning of the present investigation, only a few of the simplest, nonfunctionalized representatives of such types of compounds have been described. It was shown recently in our laboratory [16][17][18][19] that thiophosphoryl compounds 1, with the phosphorus atom bearing the ω-haloalkyl moiety, rather easily undergo intramolecular S-alkylation reactions yielding fiveand six-membered 1,2-thiaphosphacyclanium salts 2. In the case of the presence of at least one alkoxy group at the phosphorus atom, a subsequent dealkylation takes place leading to formation of the 2-oxo-1,2-thiaphosphacyclanes 3 (Scheme 1).…”