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1.
Tandem radical cyclization-based strategy for the synthesis of oxa- and aza-cage compounds is described. The aryl iodides 1 and N-tosyl propargylated amine 8 lead to oxa- and aza-cages, respectively, after two tandem 5-exo-trig radical cyclizations. The alcohols 11 on reaction with nBu3SnH and AIBN give rise to the oxa-cages 14 bearing the tributyltin moiety after three tandem 5-exo-trig cyclizations. On the other hand, reaction of the propargyl ether 16 under similar conditions furnishes the oxa-cage 17 by a 5-exo-trig, 4-exo-trig, 5-exo-trig tandem radical cyclization sequence. 相似文献
2.
Jahn U 《Chemical communications (Cambridge, England)》2001,(17):1600-1601
The combination of anionic Michael addition of lithium ester enolates with radical 5-exo cyclizations through SET oxidation gives highly functionalized cyclopentanes. 相似文献
3.
The first one-step conversions of ketimines I into cyclized allylamine derivatives of types II and III are reported. 相似文献
4.
J.S. Yadav K. Vishweshwar Rao M. Sridhar Reddy A.R. Prasad 《Tetrahedron letters》2006,47(26):4393-4395
An efficient and flexible approach for the total synthesis of (−)-tetrahydrolipstatin is described. The main features of the synthetic strategy are a stereocontrolled radical cyclization and the successful utilization of commercially available S-malic acid. 相似文献
5.
A practical and efficient method for the preparation of silaheterocycles is described. The key step involves the initial formation of symmetrical chiral ditopic ligand, N,N′‐1,2‐cyclohexylenebis(salicylideneimine) followed by sequential deprotonation with NaH to form dianion intermediate, which reacts with diorganodichlorosilanes to furnish dibenzodioxadiazasilamacrocycles. The products were characterized by satisfactory elemental analyses and spectral (IR, 1H, 13C, 29Si NMR, and Mass) studies. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:455–460, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20460 相似文献
6.
An efficient strategy for the stereoselective construction of unsymmetrical dioxa-cage compounds containing ether linkages employing a 6-exo-trig alkyl radical cyclization to vinylogous carbonates is developed. The radical precursors are prepared from the diols obtained from the Diels-Alder adducts via iodoetherification followed by addition of the alcohol to the ethyl propiolate. The geometrical constrains play important role in deciding the outcome of the reaction as cyclization versus simple reduction. Formation of the mono-oxa-cage compounds via a 5-exo-trig intramolecular alkyl radical cyclization to olefin is also described. The dioxa-cages could also be assembled employing a tandem oxymercuration reduction-radical cyclization to vinylogous carbonates protocol with equal efficiency and with reduced number of steps. 相似文献
7.
《Tetrahedron letters》1988,29(8):897-900
A general procedure for cyclopentane synthesis based on free-radical cyclization of thioacetals is described. This permits the rapid assembly, by intramolecular annulation, of various ring systems bearing useful functionality for use in total synthesis. 相似文献
8.
Elena M. Sánchez 《Tetrahedron》2008,64(22):5111-5118
Sulfanyl radicals trigger a tandem addition-cyclization protocol in linalool or citronelene derivatives for the efficient construction of the iridane monoterpene skeleton. Best results in yields and diastereoselectivity were obtained when phenylethylsulfanyl was used as radical initiator. We have proved the utility of this protocol with the enantiospecific synthesis of natural iridane dehydroiridomyrmecin starting from a (−)-linalyl acetate ester derivative in five steps with a 28% overall yield. 相似文献
9.
The use of vinyl radical cyclization in the simplification of synthesis design is probed with the sesquiterpene seychellene as a target. The construction is particularly effective because of very high stereoselectivity in the alkylation of a 2,2,2-bi- cyclo-5-octene-2-one system and because of the control offered by the specific location of the double bond in the product of the vinyl radical cyclization. 相似文献
10.
[reaction: see text] A synthesis of 28, the carbon framework of the eleutherobin aglycone, is reported in a 15-step sequence from readily available starting materials. The tandem Diels-Alder reaction of 6 and 7 to produce 18, in which three new rings and six new stereocenters are formed, is a key step in the reaction sequence. 相似文献
11.
12.
A new, efficient, high yielding method for the synthesis of benzoxocine derivatives has been developed via a thiophenol-mediated intramolecular 8-endo radical cyclization. This method allowed the synthesis of the backbone of several sesquiterpenes. 相似文献
13.
Jonathan Clayden Katherine R. Hebditch Benjamin Read Madeleine Helliwell 《Tetrahedron letters》2007,48(48):8550-8553
The addition of tin or silicon nucleophiles to bicyclic enones generated by dearomatising cyclisation gives stannanes and silanes stereoselectively. These compounds may be fragmented under oxidative conditions to generate substituted pyrrolidines bearing C2 and C3 substituents closely related to those found in the kainoid series of cyclic amino acids. 相似文献
14.
Daniel Kaufmann Peter C. Fünfschilling Ulrich Beutler Pascale Hoehn Olivier Lohse Werner Zaugg 《Tetrahedron letters》2004,45(27):5275-5278
A novel, simple, and straightforward process for the large-scale synthesis of oxcarbazepine, the active ingredient of Trileptal®, a medicine for the treatment of epilepsy, has been developed. Starting from readily available 1,3-dihydro-1-phenyl-2H-indol-2-one, a Friedel-Crafts cyclization strategy provides a direct route to the tricyclic framework of the target molecule. Crucial to the success of the strategy was the choice of the proper nitrogen-protecting group. 相似文献
15.
Synthesis of 2-benzazepines was readily achieved via 7-endo radical cyclization of N-o-bromobenzylitaconamides or N-o-bromobenzylmethacrylamides which were prepared in two steps from commercially available benzaldehydes, amines, and alpha,beta-unsaturated acids. 相似文献
16.
Masaru Terauchi 《Tetrahedron letters》2005,46(38):6555-6558
An efficient method for preparing β-C-glucosides using radical cyclization with a temporary connecting silicon tether was developed. In this reaction, conformational restriction of the substrates to the unusual 1C4-form is essential for the cyclization to occur. 相似文献
17.
Sutapa Ray 《Tetrahedron》2008,64(14):3253-3267
A Hauser-initiated tandem annulation has been developed for the rapid regiospecific synthesis of benzonaphthopyranones via formation of two rings in one-pot operation. This strategy has been generalized with benzonaphthopyranones 26, 29, 32, and 35. It has also been employed in a short synthesis of chartarin (3) and O-methylhayumicinone (67). 相似文献
18.
The biological activity of unsaturated iminosugars has not yet been extensively studied because of a lack of general synthetic methods. A practical synthesis of these cyclic ketimine sugars was developed, which was based on a tandem addition-cyclization reaction of a Grignard reagent to a omega-methanesulfonylglycononitrile. 相似文献
19.
Wang H Zhao YL Ren CQ Diallo A Liu Q 《Chemical communications (Cambridge, England)》2011,47(45):12316-12318
A new strategy for the rapid construction of functionalized reduced indoles starting from activated methylene isocyanides and 1,5-dielectrophilic 5-oxohepta-2,6-dienoates (and their equivalents) through a [5+1] annulation-isocyanide cyclization cascade under basic conditions has been developed. This strategy allows the synthesis of polysubstituted dihydroindolones and tetrahydroindolones in high to excellent yields under extremely mild conditions in a single step. 相似文献
20.
[reaction: see text] Organoselenium precursors of 3-aza-5-hexenyl radicals carrying a 1-hydroxyalkyl group in the 2-position were prepared by addition of organometallic reagents to N-allyl-2-aziridinecarbonitrile, reduction of the resulting aziridine ketone, and regioselective benzeneselenol ring opening of the aziridine. Reductive radical cyclization was highly selective, affording the corresponding trans-2,4-disubstituted pyrrolidine (cis/trans ca. 1/10) as the major diastereomer. Recrystallization afforded material that was substantially more enriched in the trans isomer (cis/trans < 1/25). 相似文献