Showing papers on "Ferrier rearrangement published in 2011"

Gold‐Catalyzed Tandem Intramolecular Heterocyclization/Petasis–Ferrier Rearrangement of 2‐(Prop‐2‐ynyloxy)benzaldehydes as an Expedient Route to Benzo[b]oxepin‐3(2 H)‐ones

Abstract: Partially or fully hydrogenated benzo[b]oxepines are common ring motifs found in many pharmaceutically interesting and potentially bioactive natural compounds. Representative examples range from the structurally simple and bioactive heliannuol A, pterulone, and radulanin A to the architecturally challenging compounds edulisone A and ovafolinin B. For this reason, the establishment of new synthetic methods to construct this biologically important class of compounds has received an immense amount of attention. The synthetic strategies toward functionalized benzo[b]oxepines can be divided into two groups: manipulation of a pre-existing oxygen-containing cyclic core or assembly from acyclic precursors. Despite the advances made through both these approaches, the development of new synthetic methods to prepare this class of oxygen heterocycles from readily available substrates and catalysts with selective control of substitution patterns under mild and operationally simplistic conditions remains desirable. The emergence of gold complexes as powerful and versatile Lewis acid catalysts that can mediate a plethora of C X (X=C, N, O, S) bond formations has been well documented in recent years. Among this myriad of works, one notable innovation has been the formation of carbocycles and heterocycles from cyclization of a carbonyl compound tethered to an alkyne in the presence of a gold catalyst. For example, Yamamoto and Jin recently reported an efficient synthetic route to fused triand tetracyclic enones based on the AuCl3/AgSbF6-catalyzed tandem heteroenyne metathesis/Nazarov cyclization of 1,3-enynyl ketones. On the basis of this and other previous studies on carbonyl metathesis, we reasoned that a strategy that made use of Opropargylated salicylaldehydes in the presence of a Lewis acid gold catalyst would hold promise as a new method for benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-one synthesis. As part of an ongoing program exploring the scope of gold catalysis in heterocyclic synthesis, our discovery that Au complex 3 can effect tandem intramolecular heterocyclization/Petasis–Ferrier rearrangement of 2-(prop-2-ynyloxy)benzaldehydes is reported herein (Scheme 1). This process provides a convenient synthetic route to benzo[b]oxepin-3ACHTUNGTRENNUNG(2H)-ones in 21– 99% yield for a wide variety of substrates under mild and operationally simplistic conditions that did not require the exclusion of air or moisture. A study that delineates the influence on reactivity of a substituent at the ortho position to the ethereal moiety on the salicylaldehyde is also presented. To the best of our knowledge, synthetic methods involving metal-mediated cyclizations of propargylic aldehydes of type 1 have thus far been reported to typically give the benzopyran product. We began by examining the cyclization of 1a by a variety of Lewis and Bronsted acids to establish the optimal reaction conditions (Table 1 and Table S1 in the Supporting In[a] E. M. L. Sze, Dr. W. Rao, M. J. Koh, Prof. Dr. P. W. H. Chan Division of Chemistry and Biological Chemistry School of Physical and Mathematical Sciences Nanyang Technological University Singapore 637371 (Singapore) Fax: (+65)6791-1961 E-mail : waihong@ntu.edu.sg Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201003096. Scheme 1. Gold(I)-catalyzed synthesis of benzo[b]oxepin-3 ACHTUNGTRENNUNG(2H)-ones from 2-(prop-2-ynyloxy)benzaldehydes. R=H, alkyl, aryl, halide, or NO2; R , R=H or alkyl.

Gold(I)-catalyzed access to tetrahydropyran-4-ones from 4-(alkoxyalkyl)oxy-1-butynes: formal catalytic Petasis-Ferrier rearrangement.

Abstract: Substituted tetrahydropyranones are synthesized by the new method including a gold(I)-catalyzed cycloisomerization which represents a catalytic alternative of the Petasis—Ferrier rearrangement.

Environmentally Benign Synthesis of 2,3-Unsaturated Glycopyranosides in Task-Specific Ionic Liquid

Abstract: A green reaction condition has been developed for the synthesis of 2,3-unsaturated glycopyranosides by the Ferrier rearrangement of glycals using alcohols and thiols in 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM]·OTf) in excellent yield. [BMIM]·OTf has been applied as a task specific ionic liquid organo-catalyst. Operational simplicity, environmentally benign reaction condition, use of task specific ionic liquid, short reaction time, high yields are the notable features of this methodology.

Method for preparing 4, 6-dibenzyl-2, 3-unsaturated glucoside

Abstract: The invention discloses a method for preparing 4, 6-dibenzyl-2, 3-unsaturated glucoside, which is characterized by comprising the following steps of: mixing 3, 4, 6-tri-O-benzyl glucal and dichloromethane, acetonitrile, tetrahydrofuran, N, N-dimethylformamide, acetone or diethyl ether in a molar volume ratio of 1 mol: (5-50) L, adding a sulfuric acid/silica catalyst and an oxygen- or sulfur-containing nucleophilic receptor under stirring, undergoing a rearrangement reaction of 3, 4, 6-tri-O-benzyl glucal at a temperature of 0-50 DEG C, filtering out the catalyst after the reaction ends, and concentrating the filter liquor to obtain the 4, 6-dibenzyl-2, 3-unsaturated glucoside. The method for preparing the 4, 6-dibenzyl-2, 3-unsaturated glucoside has the advantages of simple process, convenience in operating, high yield, low production cost and no environmental pollution; the reagent used for synthesis is cheap and easy to get; the dissolvent is cheap and easy to get and has little toxicity; and the method for preparing the 4, 6-dibenzyl-2, 3-unsaturated glucoside is a method for an Ferrier rearrangement reaction of 3, 4, 6-tri-O-benzyl glucose ene with a very good application prospect.

Gold(I)-Catalyzed Access to Tetrahydropyran-4-ones from 4-(Alkoxyalkyl)oxy-1-butynes: Formal Catalytic Petasis—Ferrier Rearrangement.

Abstract: Substituted tetrahydropyranones are synthesized by the new method including a gold(I)-catalyzed cycloisomerization which represents a catalytic alternative of the Petasis—Ferrier rearrangement.

A Modular, Efficient, and Stereoselective Synthesis of Substituted Piperidin‐4‐ols.

Abstract: The convenient one-pot procedure involves Au-catalyzed cyclization of amides, chemoselective reduction and spontaneous Ferrier rearrangement.