Y(OTf) 3 catalyzed substitution dependent oxidative C(sp 3 )eC(sp 3 ) cleavage and regioselective dehydration of b-allyl- b-hydroxydithioesters: alternate route to a,b-unsaturated ketones and functionalized dienes Sushobhan Chowdhury a , Tanmoy Chanda a , Ganesh Chandra Nandi b , Suvajit Koley a , B. Janaki Ramulu a , S.K. Pandey c , Maya Shankar Singh a, * a Department of Chemistry, Faculty of Science, Banaras Hindu University, Varanasi 221005, India b Department of Chemistry, University of North Florida, 1 UNF Drive, Jacksonville, FL 32224, USA c School of Chemistry and Biochemistry, Thapar University, Patiala 147004, India article info Article history: Received 22 June 2013 Received in revised form 18 July 2013 Accepted 30 July 2013 Available online 5 August 2013 Keywords: Regioselective allylation Yttrium(III)triflate CeC activation and cleavage Allylic isomerization a,b-Unsaturated ketone Selective dehydration Functionalized diene abstract b-Allyl-b-hydroxydithioesters have been generated by the regioselective Grignard addition to the b- oxodithioesters. They have been successfully employed in selective C(sp 3 )eC(sp 3 ) bond cleavage to construct a,b-unsaturated ketone residues by the treatment of an emerging catalyst yttrium(III)triflate for the first time. On the other hand, hetaryl substituted b-allyl-b-hydroxydithioesters led to the useful diene precursors through selective dehydration under the similar conditions. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The synthesis of important molecular structures has always been the primary motto of organic synthesis. The total synthesis of a molecule primarily needs the construction of the parts of its framework. The architectural strategy to achieve the frameworks includes fusion of small fragments to a large one or vice versa, i.e., the cleavage of fragments from a large skeleton until the access of the desired fragment residue becomes possible. Both ways are of equal synthetic importance. Fragmentation methodologies, espe- cially, which are achieved by selective CeC bond activation, will certainly demand a prior significance due to the well-known in- ertness of the CeC bond. Tertiary alcohols in several cases have proven themselves suitable for CeC bond cleavage strategy. For this purpose, one established approach involves the b-alkyl elimination via an alkoxy-metal intermediate of various strained as well as unstrained tertiary alcohol analogues. 1,2 Further, transition-metal complexes have well been utilized for the purpose. 3 Namely, Kondo et al. have achieved b-allyl cleavage in open chain un- strained tertiary homoallyl alcohol employing Ru complexes as catalyst. 1a Rare-earth metal triflates are new type of Lewis acid catalysts, which are playing vital roles in various organic transformations. 4 Of them yttrium poses very specific coordination property by virtue of which its complexes like Y(OTf) 3 have become a well established catalyst in polymer science where it is mainly used to increase the stereoregularity of polymers. 5 In spite of its tremendous use in polymer, there exists only few examples of Y(OTf) 3 to catalyze traditional organic transformations. 4def This time, we disclose the maiden example of selective cleavage of C(sp 3 )eC(sp 3 ) bond from b-allyl-b-hydroxydithioesters catalyzed by Y(OTf) 3 . Furthermore, we have unveiled the highly selective dehydration in case of 2- thiophenyl and 2-furyl substituted b-allyl-b-hydroxydithioesters. a,b-Unsaturated carbonyl groups are important structural units in a number of biologically active compounds, as well as ubiquitous structural motifs to various organic transformations. Some specific * Corresponding author. Tel./fax: þ91 (0)542 6702502; e-mail addresses: mssinghbhu@yahoo.co.in, mayashankarbhu@gmail.com (M.S. Singh). Contents lists available at ScienceDirect Tetrahedron journal homepage: www.elsevier.com/locate/tet 0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.tet.2013.07.092 Tetrahedron 69 (2013) 8899e8903