@article { ISI:000237651600007, title = {Palladium mediated cycloisomerization of sugar alkynols: synthesis of cyclic enol-ethers and spiroketals}, journal = {Tetrahedron Letters}, volume = {47}, number = {22}, year = {2006}, month = {MAY}, pages = {3649-3652}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Functionalized bicyclic enol-ethers and spiroketals are prepared by Pd catalyzed cycloisomerization of 3-C-alkynylfuranosyl derivatives. Cycloisomerization of differently substituted alkyne derivatives revealed a preference for 6-endo-dig cyclization over 5-exo-dig if the substituent is not sufficiently electron withdrawing. The scope of these cycloisomerizations has been further extended by integrating with conjugate addition. (c) 2006 Elsevier Ltd. All rights reserved.

}, keywords = {c-alkynylfuranose, cycloisomerization, enol-ether, Palladium, Spiroketal}, issn = {0040-4039}, doi = {10.1016/j.tetlet.2006.03.143}, author = {Ramana, C. V. and Mallik, Rosy and Gonnade, Rajesh G. and Gurjar, Mukund K.} } @article { ISI:000254901800024, title = {Influence of electronic factors on palladium-mediated cycloisomerization: a systematic investigation of competitive 5-exo-dig versus 6-endo-dig cyclizations of sugar alkynols}, journal = {Tetrahedron}, volume = {64}, number = {1}, year = {2008}, month = {JAN}, pages = {219-233}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, type = {Article}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Pd-mediated cycloisomerization of 3-C-alkynyl-allo- and ribofuranose derivatives was investigated in detail to understand the influence of electronic factors on the regioselectivity in ring closure reaction. The reactions in general are influenced by the electronic nature of the substituent on the alkyne unit. A preference for endo-dig cyclization over exo-dig is noted, if the alkynyl substituent is not sufficiently electron withdrawing, (c) 2007 Elsevier Ltd. All rights reserved.

}, keywords = {C-alkynyl furanose, cycloisomerization, enol ether, Palladium, Spiroketal}, issn = {0040-4020}, doi = {10.1016/j.tet.2007.10.072}, author = {Ramana, C. V. and Mallik, Rosy and Gonnade, Rajesh G.} } @article { ISI:000271713300024, title = {Influence of electronic factors on pd-mediated cycloisomerization: a systematic investigation of competitive 6-exo-dig versus 7-endo-dig cyclizations of sugar alkynols}, journal = {Tetrahedron}, volume = {65}, number = {47}, year = {2009}, month = {NOV}, pages = {9819-9832}, publisher = {PERGAMON-ELSEVIER SCIENCE LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND}, abstract = {

Pd-mediated cycloisomerization of 3-C-propargyl-ribo- and allofuranose derivatives was investigated in detail to understand the influence of electronic factors on the regioselectivity (6-exo- vs 7-endo) of alkynol cycloisomerization leading either to a six- or seven-membered ring. In general, the 6-exo-dig mode of cyclization is facile and is independent of electronic factors. With some of the alkynols, a regioselective (7-endo?) hydration of the alkyne unit was observed and this has been attributed to the participation of C(3)-OH. When the C(3)-OH was protected as its benzyl ether, cycloisomerization of these alkynols occurred exclusively in a 6-exo-dig mode resulting in the corresponding [3.2.1]-bicyclic ketals. Additional control experiments conducted were in support of the participation of C(3)-OH in regioselective alkyne hydration. (C) 2009 Elsevier Ltd. All rights reserved.

}, keywords = {Alkynol cycloisomerization, Bridged bicyclic ketal, Palladium, Sonogashira coupling, Sugar alkynol}, issn = {0040-4020}, doi = {10.1016/j.tet.2009.09.071}, author = {Ramana, C. V. and Induvadana, Boddeti and Srinivas, Burgula and Yadagiri, Kommagalla and Deshmukh, Madhusudhan N. and Gonnade, Rajesh G.} } @article {49411, title = {Palladium-catalyzed regioselective C(4)-H fluoroalkoxylation of indoles through weak chelation assistance}, journal = {ChemCatChem}, year = {2024}, month = {OCT}, type = {Article; Early Access}, abstract = {

Installing fluoroalkyl motifs into biorelevant indoles is particularly interesting due to their ubiquitous presence in drug molecules. Herein, we demonstrate the regioselective C4 fluoroalkoxylation of indoles using fluoroalcohols via palladium-catalyzed chelation-assisted C \& horbar;H activation. The weak chelating benzoyl moiety at the C3 position acts as a directing group for remote C(4)\& horbar;H fluoroalkoxylation of diversely substituted indoles. This methodology demonstrates a high level of regioselectivity and tolerates a range of crucial functional groups, yielding diverse trifluoroalkoxylated indoles in moderate to good yields. Removal of directing/protecting groups and further functionalization established the synthetic utility of the methodology. A preliminary mechanistic investigation is conducted by isolating the palladacycle intermediate and performing the deuterium scrambling study. The regioselective C4 fluoroalkoxylation of indoles with various fluoroalcohols is achieved by the palladium-catalyzed weak chelation assistance strategy. The reaction is compatible for a range of important functionalities and proceeds via the intermediacy of a six-membered palladacycle following a Pd(II)/Pd(IV) pathway. image

}, keywords = {C-H activation, indoles, Palladium, Regioselective, Trifluoroalkoxylation}, issn = {1867-3880}, doi = {10.1002/cctc.202401188}, author = {Vijaykumar, Muniyappa and Gonnade, Rajesh G. and Punji, Benudhar} }