Willem Verboom - Academia.edu (original) (raw)
Papers by Willem Verboom
Recueil des Travaux Chimiques des Pays-Bas, Sep 2, 2010
The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and... more The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and methyl propynoate 2, react, under the influence of pyrrolidine via the α‐[(1‐pyrrolidinyl)methylene]cycloalkeneacetates (Z)‐4, (Z)‐7, (Z)‐11 and (Z)‐14, to give the corresponding E isomers. The structure of (E)‐7 has been unequivocally established by X‐ray analysis. The formation of (E)‐4, (E)‐7, (E)‐11 and (E)‐14 can be explained by the sequence: Michael addition, elimination, conrotatory ring opening, followed by Z/E isomerization. In the cases involving a relatively slow reaction (10, 13) and, in addition, the presence of an excess of pyrrolidine, the enamines 9, 16 and the propenoate 12 could also be detected. The formation of 12 can be rationalized by a Michael addition of pyrrolidine to methyl propynoate (2), formed by a retro (2 + 2) cycloaddition.
Acta Crystallographica Section C-crystal Structure Communications, Nov 15, 1998
A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique mole... more A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique molecules are in virtually the same conformation and are related by a local inversion centre; the other two molecules each have a different conformation. The structure contains a number of short C-H-.. 7r contacts.
Recueil des Travaux Chimiques des Pays-Bas, Sep 2, 2010
The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and... more The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and methyl propynoate 2, react, under the influence of pyrrolidine via the α‐[(1‐pyrrolidinyl)methylene]cycloalkeneacetates (Z)‐4, (Z)‐7, (Z)‐11 and (Z)‐14, to give the corresponding E isomers. The structure of (E)‐7 has been unequivocally established by X‐ray analysis. The formation of (E)‐4, (E)‐7, (E)‐11 and (E)‐14 can be explained by the sequence: Michael addition, elimination, conrotatory ring opening, followed by Z/E isomerization. In the cases involving a relatively slow reaction (10, 13) and, in addition, the presence of an excess of pyrrolidine, the enamines 9, 16 and the propenoate 12 could also be detected. The formation of 12 can be rationalized by a Michael addition of pyrrolidine to methyl propynoate (2), formed by a retro (2 + 2) cycloaddition.
![Research paper thumbnail of Selective phosphorylation of p-tert-butylcalix[6]arene](https://attachments.academia-assets.com/118236941/thumbnails/1.jpg)
](Journal of the Chemical Society, 1993
Acta Crystallographica Section C-crystal Structure Communications, Nov 15, 1998
A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique mole... more A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique molecules are in virtually the same conformation and are related by a local inversion centre; the other two molecules each have a different conformation. The structure contains a number of short C-H-.. 7r contacts.
Journal of the American Chemical Society, 1994
![Research paper thumbnail of Selective phosphorylation of p-tert-butylcalix[6]arene](https://attachments.academia-assets.com/118236934/thumbnails/1.jpg)
](Journal of the Chemical Society, 1993
Chemistry: A European Journal, Sep 17, 2010
Journal of the American Chemical Society, 1994
The Journal of Organic Chemistry, 1991
Enantiomerically pure dihydropyrimidinone 1 reacts with aryl iodides in the presence of catalytic... more Enantiomerically pure dihydropyrimidinone 1 reacts with aryl iodides in the presence of catalytic amounts of Pd(OAc)2 and added phosphine to afford dihydropyrimidinone 4, in which a formal conjugate addition of the aryl group to the a,@-unsaturated system has occurred. Application of this methodology to the synthesis of a protected version of the tripeptide portion of the natural product jasplakinolide is presented.
Chemistry: A European Journal, Sep 17, 2010
![Research paper thumbnail of Self-reproduction of chirality in carbon-carbon bond formation via dipolar intermediates generated in situ by [1,5] hydrogen transfer](https://attachments.academia-assets.com/118236968/thumbnails/1.jpg)
](Journal of the American Chemical Society, May 1, 1987
this paper represents one of the very few known photochemical reactions involving reduced flavin.... more this paper represents one of the very few known photochemical reactions involving reduced flavin. Other examples include the photoalkylation of reduced flavin bound to lactate oxidase32 and the photodehalogenation reactions observed with reduced 7-and 8-halogen-substituted flavins.33 Acknowledgment. We thank Drs. Wallace Ashton and Franz Muller for gifts of 1-deazariboflavin and 7,8-dimethyl-1 ,loethyleneisoalloxazium perchlorate, respectively. We are grateful to Dr. Richard Rest for the use of HPLC equipment. We also thank Juanita Yee-Foon Peck for skilled technical assistance.
Chemischer Informationsdienst, Mar 8, 1983
ChemInform Abstract Cycloaddition von Acetylendicarbonsäuredimethylester an das Cyclohexenylpyrro... more ChemInform Abstract Cycloaddition von Acetylendicarbonsäuredimethylester an das Cyclohexenylpyrrolidin (Ia) gibt entgegen Literaturangaben nicht nur das Cycloaddukt (IIa), sondern auch das cis,trans-Dien (IIIa), das sich schliesslich zum stabileren cis,cis-Isomeren IVa) umlagert. Die gleiche Cycloaddition mit dem Thiopyranylpyrrolidin (Ib) ergibt (IIIb), das in Pl mit Z=2 kristallisiert und sich in siedendem MeOH zu (IVb) und einem Pyrrolizin als Folgeprodukt von (IIb) umlagert. Die Cycloaddition an (Ic) und (Id) schliesslich gibt die is,trans-Diene (IIIc) und (IIId). Damit ist nachgewiesen, dass die Ringöffnung von cis-verbundenen 3-Amino-cyclobutenen vom Typ (II) konrotatorisch zu gespannten cis,trans-Dienen vom Typ (III) verläuft, was die Revision von Strukturzuordnungen bei einer Reihe von erbindungen sowie von stereochemischen Angaben verschiedener Autoren erforderlich macht. Photochemisch lagert sich (IIIb) in (V) um, was die Bildung von "abnormen" Ringöffnungsprodukten dieses Typs aus Verbindungen vom Typ (II) alsüber cis,trans-Isomere wie (III) und anschliessende [l,5]H-Verschiebung erklärt.
ChemInform, Aug 17, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
![Research paper thumbnail of Aggregates of calix[4]arenes based on the 2,6-diaminotriazine · imide system](https://attachments.academia-assets.com/118236918/thumbnails/1.jpg)
](Recueil des Travaux Chimiques des Pays-Bas, Sep 2, 2010
ChemInform, Aug 20, 2010
ChemInform Abstract Aus Bis-O-thiocarbonyl-disulfiden (I) und Triphenylphosphin (II) entstehen Sa... more ChemInform Abstract Aus Bis-O-thiocarbonyl-disulfiden (I) und Triphenylphosphin (II) entstehen Salze (III), die z.B. mit dem Monophosphat (IV)über Zwischenstufen wie (V) Zum gemischten Ester (VI) führen.Die Reaktion wird für verschiedene Alkylierungsmittel sowie Lösungsmittel untersucht und in ihrer Ausbeute optimiert.
ChemInform, Nov 8, 2005
"..... these substances contain a small quantity of a strongly radioactive body, differing from u... more "..... these substances contain a small quantity of a strongly radioactive body, differing from uranium and thorium and the simple bodies actually known. I thought that if this were indeed the case, I might hope to extract this substance by the ordinary methods of chemical analysis" Mme. Curie Aan Lieke, Sven en Zoë Contents Chapter 1 General Introduction Chapter 2 Naturally Occurring Radioactive Ra 2+ Nuclides in Waste Streams and their Removal 2.1 Introduction and Dimethoxythiacalix[4]monocrowns 42 3.3 Conclusions 45 3.4 Experimental References 54 Chapter 4 Ionizable (Thia)calix[4]crowns as Highly Selective Ra 2+ Extractants 57 4.1 Introduction 4.2 Results and Discussion 4.2.1 Synthesis 4.2.2 Extraction of Alkali(ne Earth) Cations by (Thia)calix[4]crown Dicarboxylic Acids 60 4.2.3 Precipitation of Ra 2 + 61 4.2.4 Competitive Ra 2+ Extraction Experiments in the Presence of Alkali and Alkaline Earth Cations 63 4.2.5 Dissolution of Precipitated Ra 2+ Salts 4.2.6 Effective pH Range of Thiacalix[4]crown-6 Dicarboxylic Acid 68 4.2.7 Loading and Regeneration of Thiacalix[4]crown-6 Dicarboxylic Acid by pH Variation 4.3 Conclusions 4.4 Experimental 4.4.1 Synthesis ii 4.4.2 Extraction References 76 Chapter 5 Thiacalix[4]arene Derivatives as Ra 2+ Extractants: a Systematic Study on the Requirements for Ra 2+ Extraction 79 Chapter 2 Naturally Occurring Radioactive Ra 2+ Nuclides in Waste Streams and their Removal by Selective extraction
ChemInform, Aug 15, 1989
ChemInform Abstract The dialkylaminobenzoquinone (I) undergoes thermal cyclization to form the py... more ChemInform Abstract The dialkylaminobenzoquinone (I) undergoes thermal cyclization to form the pyrrolo(1,2-α)indoles (II). In similar reactions, the naphthoquinones (III) and (V) are converted to the corresponding pyrrolo(1,2-α)indoles (IV) and the pyrido(1,2-α)indoles (VI). Related naphthohydroquinone ethers do not perform this ring closure reaction. The synthesis of the starting materials is described in the original paper. (Mechanism).
ChemInform, Aug 20, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Recueil des Travaux Chimiques des Pays-Bas, Sep 2, 2010
The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and... more The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and methyl propynoate 2, react, under the influence of pyrrolidine via the α‐[(1‐pyrrolidinyl)methylene]cycloalkeneacetates (Z)‐4, (Z)‐7, (Z)‐11 and (Z)‐14, to give the corresponding E isomers. The structure of (E)‐7 has been unequivocally established by X‐ray analysis. The formation of (E)‐4, (E)‐7, (E)‐11 and (E)‐14 can be explained by the sequence: Michael addition, elimination, conrotatory ring opening, followed by Z/E isomerization. In the cases involving a relatively slow reaction (10, 13) and, in addition, the presence of an excess of pyrrolidine, the enamines 9, 16 and the propenoate 12 could also be detected. The formation of 12 can be rationalized by a Michael addition of pyrrolidine to methyl propynoate (2), formed by a retro (2 + 2) cycloaddition.
Acta Crystallographica Section C-crystal Structure Communications, Nov 15, 1998
A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique mole... more A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique molecules are in virtually the same conformation and are related by a local inversion centre; the other two molecules each have a different conformation. The structure contains a number of short C-H-.. 7r contacts.
Recueil des Travaux Chimiques des Pays-Bas, Sep 2, 2010
The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and... more The (2 + 2) cycloadducts 3, 6, 10 and 13, derived from pyrrolidine enamines of cyclic ketones and methyl propynoate 2, react, under the influence of pyrrolidine via the α‐[(1‐pyrrolidinyl)methylene]cycloalkeneacetates (Z)‐4, (Z)‐7, (Z)‐11 and (Z)‐14, to give the corresponding E isomers. The structure of (E)‐7 has been unequivocally established by X‐ray analysis. The formation of (E)‐4, (E)‐7, (E)‐11 and (E)‐14 can be explained by the sequence: Michael addition, elimination, conrotatory ring opening, followed by Z/E isomerization. In the cases involving a relatively slow reaction (10, 13) and, in addition, the presence of an excess of pyrrolidine, the enamines 9, 16 and the propenoate 12 could also be detected. The formation of 12 can be rationalized by a Michael addition of pyrrolidine to methyl propynoate (2), formed by a retro (2 + 2) cycloaddition.
Journal of the Chemical Society, 1993
Acta Crystallographica Section C-crystal Structure Communications, Nov 15, 1998
A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique mole... more A triclinic modification of triphenylphosphine, C~8H15P, is reported. Two of the four unique molecules are in virtually the same conformation and are related by a local inversion centre; the other two molecules each have a different conformation. The structure contains a number of short C-H-.. 7r contacts.
Journal of the American Chemical Society, 1994
Journal of the Chemical Society, 1993
Chemistry: A European Journal, Sep 17, 2010
Journal of the American Chemical Society, 1994
The Journal of Organic Chemistry, 1991
Enantiomerically pure dihydropyrimidinone 1 reacts with aryl iodides in the presence of catalytic... more Enantiomerically pure dihydropyrimidinone 1 reacts with aryl iodides in the presence of catalytic amounts of Pd(OAc)2 and added phosphine to afford dihydropyrimidinone 4, in which a formal conjugate addition of the aryl group to the a,@-unsaturated system has occurred. Application of this methodology to the synthesis of a protected version of the tripeptide portion of the natural product jasplakinolide is presented.
Chemistry: A European Journal, Sep 17, 2010
Journal of the American Chemical Society, May 1, 1987
this paper represents one of the very few known photochemical reactions involving reduced flavin.... more this paper represents one of the very few known photochemical reactions involving reduced flavin. Other examples include the photoalkylation of reduced flavin bound to lactate oxidase32 and the photodehalogenation reactions observed with reduced 7-and 8-halogen-substituted flavins.33 Acknowledgment. We thank Drs. Wallace Ashton and Franz Muller for gifts of 1-deazariboflavin and 7,8-dimethyl-1 ,loethyleneisoalloxazium perchlorate, respectively. We are grateful to Dr. Richard Rest for the use of HPLC equipment. We also thank Juanita Yee-Foon Peck for skilled technical assistance.
Chemischer Informationsdienst, Mar 8, 1983
ChemInform Abstract Cycloaddition von Acetylendicarbonsäuredimethylester an das Cyclohexenylpyrro... more ChemInform Abstract Cycloaddition von Acetylendicarbonsäuredimethylester an das Cyclohexenylpyrrolidin (Ia) gibt entgegen Literaturangaben nicht nur das Cycloaddukt (IIa), sondern auch das cis,trans-Dien (IIIa), das sich schliesslich zum stabileren cis,cis-Isomeren IVa) umlagert. Die gleiche Cycloaddition mit dem Thiopyranylpyrrolidin (Ib) ergibt (IIIb), das in Pl mit Z=2 kristallisiert und sich in siedendem MeOH zu (IVb) und einem Pyrrolizin als Folgeprodukt von (IIb) umlagert. Die Cycloaddition an (Ic) und (Id) schliesslich gibt die is,trans-Diene (IIIc) und (IIId). Damit ist nachgewiesen, dass die Ringöffnung von cis-verbundenen 3-Amino-cyclobutenen vom Typ (II) konrotatorisch zu gespannten cis,trans-Dienen vom Typ (III) verläuft, was die Revision von Strukturzuordnungen bei einer Reihe von erbindungen sowie von stereochemischen Angaben verschiedener Autoren erforderlich macht. Photochemisch lagert sich (IIIb) in (V) um, was die Bildung von "abnormen" Ringöffnungsprodukten dieses Typs aus Verbindungen vom Typ (II) alsüber cis,trans-Isomere wie (III) und anschliessende [l,5]H-Verschiebung erklärt.
ChemInform, Aug 17, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Recueil des Travaux Chimiques des Pays-Bas, Sep 2, 2010
ChemInform, Aug 20, 2010
ChemInform Abstract Aus Bis-O-thiocarbonyl-disulfiden (I) und Triphenylphosphin (II) entstehen Sa... more ChemInform Abstract Aus Bis-O-thiocarbonyl-disulfiden (I) und Triphenylphosphin (II) entstehen Salze (III), die z.B. mit dem Monophosphat (IV)über Zwischenstufen wie (V) Zum gemischten Ester (VI) führen.Die Reaktion wird für verschiedene Alkylierungsmittel sowie Lösungsmittel untersucht und in ihrer Ausbeute optimiert.
ChemInform, Nov 8, 2005
"..... these substances contain a small quantity of a strongly radioactive body, differing from u... more "..... these substances contain a small quantity of a strongly radioactive body, differing from uranium and thorium and the simple bodies actually known. I thought that if this were indeed the case, I might hope to extract this substance by the ordinary methods of chemical analysis" Mme. Curie Aan Lieke, Sven en Zoë Contents Chapter 1 General Introduction Chapter 2 Naturally Occurring Radioactive Ra 2+ Nuclides in Waste Streams and their Removal 2.1 Introduction and Dimethoxythiacalix[4]monocrowns 42 3.3 Conclusions 45 3.4 Experimental References 54 Chapter 4 Ionizable (Thia)calix[4]crowns as Highly Selective Ra 2+ Extractants 57 4.1 Introduction 4.2 Results and Discussion 4.2.1 Synthesis 4.2.2 Extraction of Alkali(ne Earth) Cations by (Thia)calix[4]crown Dicarboxylic Acids 60 4.2.3 Precipitation of Ra 2 + 61 4.2.4 Competitive Ra 2+ Extraction Experiments in the Presence of Alkali and Alkaline Earth Cations 63 4.2.5 Dissolution of Precipitated Ra 2+ Salts 4.2.6 Effective pH Range of Thiacalix[4]crown-6 Dicarboxylic Acid 68 4.2.7 Loading and Regeneration of Thiacalix[4]crown-6 Dicarboxylic Acid by pH Variation 4.3 Conclusions 4.4 Experimental 4.4.1 Synthesis ii 4.4.2 Extraction References 76 Chapter 5 Thiacalix[4]arene Derivatives as Ra 2+ Extractants: a Systematic Study on the Requirements for Ra 2+ Extraction 79 Chapter 2 Naturally Occurring Radioactive Ra 2+ Nuclides in Waste Streams and their Removal by Selective extraction
ChemInform, Aug 15, 1989
ChemInform Abstract The dialkylaminobenzoquinone (I) undergoes thermal cyclization to form the py... more ChemInform Abstract The dialkylaminobenzoquinone (I) undergoes thermal cyclization to form the pyrrolo(1,2-α)indoles (II). In similar reactions, the naphthoquinones (III) and (V) are converted to the corresponding pyrrolo(1,2-α)indoles (IV) and the pyrido(1,2-α)indoles (VI). Related naphthohydroquinone ethers do not perform this ring closure reaction. The synthesis of the starting materials is described in the original paper. (Mechanism).
ChemInform, Aug 20, 2010
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.