Donna Van Engen

Synthesis and X-ray crystallographic characterization of a (1,3,5)cyclophane with three amide N-H groups surrounding a central cavity. A neutral host for anion complexation

Abstract A short synthesis of 2.15.28-trioxo-3,16,29-triaza-6,19,32-trithia-[7.7.7](1,3,5)cyclophane(1) is described. An X-ray crystallographic analysis shows that the cyclophane exists in an extended conformation with three amide N-H groups directed approximately inward toward the central cavity.

Synthesis and structure of chiral macrocycles containing 2,2′-bipyridine subunits☆

A series of macrocyclic receptors has been prepared containing bipyridine groups linked to two amino acids. Variations in both the amino acid and the linking spacer have been made. The structure of the resulting macrocycles has been investigated using 1H NMR spectroscopy and X-ray crystallography. The use of L-valine leads to an open conformation for the macrocycle in which the 2-propyl substituents are directed perpendicular to the plane of the ring leaving the bipyridine and amide groups accessible for binding to a metal or complementary substrate. Proline-based macrocycles take up a twisted arrangement with the linking chain stretched across the face of the bipyridine which takes up a trans conformation. The metal ion binding properties of these derivatives have been investigated and shown to occur only to the valine macrocyles which have the two pyridine rings preorganized for complexation. These macrocycles have also been shown to bind to phenolic hydroxyl groups by using hydrogen-bond donors and acceptors from the amide groups in the linking chain.

Protonation of Fischer-type alkylidyne carbonyltungsten complexes. Structural comparison of alkylidyne and alkylidene metal complexes, including a neutron diffraction study of [W(CHCH3)Cl2(CO)(PMe3)2]

Abstract Protonation of alkylidyne tungsten complexes of the types [W(CR)Cl(CO)(PMe3)3] or [W(CR)Cl(CO)(py)(PMe3)2] with HCl affords the η2-alkylidene tungsten complexes [W(CHR)Cl2(CO)(PMe3)2] (7) (R = Me, Et, Ph, p-Tol). Protonation of the complexes [W(CR)X(CO)(CNR′)(PMe3)2] with HOSO2CF3 or HBF4 gives the alkylidene complexes [W(CHR)X(CO)(CNR′)(PMe3)2][Y] (8) (R = Me, R′ = CMe3, X = Cl, Y = CF3SO3, R = Ph, X = Cl; R′ = CMe3, Y = CF3SO3, BF4; R′ = C6H11, Y = BF4; R′ = C6H3Me2-2,6, Y = CF3SO3, R = Ph, R′ = CMe3, X = I, Y = CF3SO3, BF4). The Cue5f8H bonds of the alkylidene ligands are easily deprotonated with bases such as pyrrolidinocyclopentene or triethylamine. The solid state structures of [W(CPh)Cl(CO)(CNCMe3)(PMe3)2] (5b), [W(CHMe)Cl2(CO)(PMe3)2] (7a). [W(CHPh)Cl2(CO)(PMe3)2] (7c), and [W(CHPh)Cl(CO)(CNCMe3)(PMe3)2][BF4] (8c) were determined by X-ray crystallography. The structure of 7a was also determined by neutron diffraction. Based on the neutron diffraction data of 7a, and closely matching results from the X-ray diffraction studies, it is found that the η2-coordination mode of the alkylidene ligands gives rise to almost equal Wue5f8C(R) and Wue5f8H bond distances, 1.857(4) and 1.922(6) A, respectively, in the case of 7a. The length of the alkylidene Cue5f8H bond in 7a is 1.185(7) A. The structural comparison of 5b and 8c reveals that the protonation of the alkylidyne ligand causes the Wue5f8CPh bond to lengthen by less than 0.1 A and the Wue5f8Cue5f8Ph angle to bend by about 15°. The major induced structural change, however, may be described as a lateral shift of the CPh group by about 0.6 A away from the coordination axis defined by the extension of the Clue5f8W vector.

The synthesis and structural characterization of way-120,491; a novel potassium channel activator

Abstract The synthesis of the antihypertensive potassium channel activator WAY-120,491 (1) is described. X-ray crystallographic analysis of carbamate 15a established the 3S,4R configuration of 1. The large scale classical resolution of racemic 9 was facilitated using authentic seed crystals, whose preparation was accomplished via novel coupling of racemic azidoalcohol 17 with the putative acyltriflate 20.

Nucleotide recognition by macrocyclic receptors

It is shown that complementary positioning of recognition sites (particularly hydrogen bonding, stacking and hydrophobic groups) into a macrocyclic structure can lead to very strong and specific complexation of uncharged organic molecules.

The solid state structure of 9,11,20,22-tetraphenyltetrabenzo[a,c,l,n]pentacene-10,21-dione: A longitudinally twisted molecular ribbon

An X-ray crystallographic analysis of the title compound (1) shows that this fused-ring polycyclic molecule is greatly distorted from planarity. The structure is centrosymmetric, and the mean plane of the center ring is twisted by approximately 48° relative to the plane determined by the terminal atoms of the pentacene nucleus.

Reactions of phosphine-substituted alkylidyne carbonyltungsten complexes with dithiocarbamate ligands: Phosphine substitution and alkylidyne- carbonyl coupling

Abstract Reaction of the alkylidyne tungsten complexes cis - and trans - [W(CPh)Cl(CO) 2 (PMe 3 ) 2 ] with sodium diethyldithiocarbamate affords the ketenyl complex [W(OCCPh)(S 2 CNEt 2 )(CO)(PMe 3 ) 2 ]. Reaction of [W(CPh)Cl(CO)(PMe 3 ) 3 ] with diethyldithiocarbamate gives the dithiocarbamate-substituted alkylidyne tungsten complex [W(CPh)(S 2 CNEt 2 )(CO)(PMe 3 ) 2 ]. Reaction of cis -[W(CPh)Cl(CO) 2 (PPh 3 ) 2 ] with sodium dimethyldithiocarbamate leads to substitution of PPh 3 and formation of [W(CPh)(S 2 CNMe 2 )(CO) 2 (PPh 3 )]. The solid state structure of [W(CPh)(S 2 CNEt2)(CO)(PMe 3 ) 2 ] was determined by X-ray crystallography. Reaction of [W(CPh) (S 2 CNEt 2 )(CO)(Me 3 ) 2 ] with carbon monoxide in solution as well as in the solid state affords [W(OCCPh)( 2 CNEt2)(CO)(PMe 3 ) 2 ]. Pyrolysis of [W(OCCPh)(S 2 CNEt 2 )(CO)(PMe 3 ) 2 ] at 100°C in toluene solution gives [W(CPh)(S 2 CNEt 2 )(CO)(PMe 3 ) 2 ].

Synthesis of 3-mercapto-2(5H)-furanones via reaction of dilithio-2,4-thiazolidinedione with α-halo ketones.

Abstract A novel synthesis of 3-mercapto-2(5 H )-furanones is reported based upon the reaction of dilithio-2,4-thiazolidinedione with α-halo ketones. Substitution at the furanone 4- and 5-positions may be controlled by the choice of α-halo ketone.

Investigation of the dithiocarbamate-induced coupling of allylidene and carbonyl ligands on a tungsten center

Abstract Reaction of the allylidene tungsten complex [W(CPhCHCHMe)Br 2 (CO) 2 (4-picoline)] ( 1 ) with the dithiocarbamates MS 2 CNR 2 ( a : M=Na, R=Et; b : M=Na, R=Me; c : M=Li, R=Ph) in THF at 50 °C affords the vinylketene tungsten complexes [W(S 2 CNR 2 ) 2 (OCCPhCHCHMe)(CO)] ( 2a–c ). At lower temperatures, four reaction intermediates ( 3–6 ) may be discerned. Spectroscopic studies indicate that these compounds contain η 4 -allyldithiocarbamate ligands which are generated by addition of dithiocarbamate across the metal-carbon double bond of the allylidene-tungsten unit in 1 . The structures of [W(S 2 CNEt 2 ) 2 (OCCPhCHCHMe)(CO)] ( 2a ) and of one intermediate, [W(η 4 -Et 2 NCS 2 CPhCHCHMe)(S 2 CNEt 2 )(CO) 2 ] ( 5a ) were elucidated by X-ray crystallography.

A novel isomerization reaction of tricyclo[5.2.1.02,6]decane

Abstract HNO 3 -catalyzed isomerization of tricyclo[5.2.1.0 2,6 ]decane affords tricyclo[4.2.2.0 1,5 ]decane - the “bottle neck” in the adamantane rearrangement.