Molecules

Open AccessArticle

Cohalogenation of Allyl and Vinylsilanes using Polymer-bound Haloate(I)-Reagents

by Silvie Domann, Georgia Sourkouni-Argirusi, Nuria Merayo, Andreas Schönberger and

Molecules 2001, 6(1), 61-66; https://doi.org/10.3390/60100061 - 16 Jan 2001

Cited by 6 | Viewed by 6894

Polymer-supported electrophilic halogenate(I) complexes 2 and 3 promote smooth addition to vinyl and allylsilanes without loss of the silyl group. In conjunction with Amberlyst A26 (OH⁻ -form) vinyl silanes are converted into epoxysilanes. Full article

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Open AccessArticle

Sensitized Photooxygenation of Cholesterol and Pseudocholesterol Derivatives via Singlet Oxygen

by Wu Shuping,

Jiang Zhiqin

, Li Heting, Yang Li and Zeng Daixun

Molecules 2001, 6(1), 52-60; https://doi.org/10.3390/60100052 - 16 Jan 2001

Cited by 10 | Viewed by 7303

Abstract

3-Substituted cholesterols and 7-substituted pseudocholesterols undergo a facile photooxygenation sensitized by 9, 10-dicyanoanthracene (DCA) and lumiflavin (LF) to give similar, oppositely-positioned enol derivatives. Both steroids showed the same reaction pattern associated with the endocyclic 5- and 4-olefin units, respectively. The reaction was proposed [...] Read more.

3-Substituted cholesterols and 7-substituted pseudocholesterols undergo a facile photooxygenation sensitized by 9, 10-dicyanoanthracene (DCA) and lumiflavin (LF) to give similar, oppositely-positioned enol derivatives. Both steroids showed the same reaction pattern associated with the endocyclic 5- and 4-olefin units, respectively. The reaction was proposed to proceed via the ene reaction of singlet oxygen and subsequent rearrangement of the initially formed 5a-hydroperoxides. Full article

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Open AccessArticle

A Simple Method for Synthesis of Active Esters of Isonicotinic and Picolinic Acids

by

Jørn B. Christensen

Molecules 2001, 6(1), 47-51; https://doi.org/10.3390/60100047 - 16 Jan 2001

Cited by 25 | Viewed by 10647

Abstract

A method for preparation of the p-nitrophenyl-, N-hydroxysuccinimidyl- and pentafluorophenyl esters of isonicotinic and picolinic acids from the corresponding acids is reported. Full article

Open AccessReview

Bile Acids as Building Blocks of Supramolecular Hosts

by

Jari Tamminen

and Erkki Kolehmainen

Molecules 2001, 6(1), 21-46; https://doi.org/10.3390/60100021 - 16 Jan 2001

Cited by 178 | Viewed by 12106

Abstract

A review of the use of bile acid-based compounds as building blocks for designing novel supramolecular hosts for molecular recognition is presented. Pharmacological applications and the newest spectroscopic and computational studies of bile acid derivatives are also shortly considered. Full article

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Open AccessArticle

Tricarbonyl(h6-Arene)Chromium(0) Complexes as Chiral Auxiliaries: Asymmetric Synthesis of b-Lactones

by

Paola Del Buttero

and Deborah Montrasio

Molecules 2001, 6(1), 13-20; https://doi.org/10.3390/60100013 - 16 Jan 2001

Cited by 4 | Viewed by 6801

Abstract

The optically pure tricarbonyl(h⁶-2-substituted benzaldehydes)chromium are used as chiral auxiliaries in the condensation with a series of doubly lithiated carboxylic acids. The intramolecular ring closure of the obtained Cr(CO)₃ complexed b-hydroxyacids affords the optically pure b-lactones in satisfactory yield. Full article

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Open AccessReview

Synthesis of Polycyclic Ring Systems Using Transition Metal Catalyzed Cyclizations of Diazo Alkynyl Ketones

by

Albert Padwa

Molecules 2001, 6(1), 1-12; https://doi.org/10.3390/60100001 - 22 Dec 2000

Cited by 24 | Viewed by 9007

Abstract

The rhodium(II)-catalyzed reaction of α-diazo ketones bearing tethered alkyne units represents a new and useful method for the construction of a variety of substituted cyclopentenones. The process proceeds by addition of the rhodium-stabilized carbenoid onto the acetylenic π-bond to give a vinyl carbenoid [...] Read more.

The rhodium(II)-catalyzed reaction of α-diazo ketones bearing tethered alkyne units represents a new and useful method for the construction of a variety of substituted cyclopentenones. The process proceeds by addition of the rhodium-stabilized carbenoid onto the acetylenic π-bond to give a vinyl carbenoid intermediate. The resulting rhodium complex undergoes a wide assortment of reactions including cyclopropanation, 1,2-hydrogen migration, CH-insertion, addition to tethered alkynes and ylide formation. When 2-alkynyl-2-diazo-3-oxobutanoates were treated with a Rh(II)-catalyst, furo[3,4-c]furans were formed in excellent yield. Full article

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