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A three-component coupling reaction was developed to access 3,3-oxyarylpropionate derivatives. Each of the three reaction components can be varied, allowing the modular synthesis of a range of important chiral building blocks.

Hydroboration using 9-BBN-H of the protected enantiomerically pure but-3-enylglycine derivative 11, prepared by copper-catalysed allylation of the serine-derived organozinc reagent 1, followed by Suzuki coupling of the derived borane with a variety of aromatic halides, 2-bromopyridine and 2-bromopropene gives the protected amino acids 14a-l and 15. This method augments our previous methods for the synthesis of phenylalanine homologues.

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Iodobenzene is shown to catalyze the 5-exo-dig cyclization of δ-alkynyl β-ketoesters under oxidative conditions that generate hypervalent iodine species in situ. The cyclopentane products contain adjacent quaternary and tertiary stereocenters which are generated with excellent diastereoselectivity.The catalytic activation of alkynes to nucleophilic addition by π-acidic metal complexes has received considerable attention from the synthetic community; 1 however there are almost no examples of such activation by organocatalysts. 2 Molecular iodine has been shown to activate alkynes to nucleophilic attack, but stoichiometric quantities of iodine are required in these cases. 3 Stoichiometric quantities of hypervalent iodine reagents are also known to activate alkynes to nucleophilic attack by heteroatoms. 4 Considering the low cost, as well as the ease of use and handling, of hypervalent iodine species compared to noble metals, the development of novel reactions utilizing these compounds is of increasing interest to synthetic chemists. 5 Notably, over the past few years, reports have appeared demonstrating the use of hypervalent iodine compounds prepared in situ from aryliodides and used as catalysts in various oxidation reactions. 6Considering that molecular iodine and hypervalent iodine mediated cyclization reactions bear similarities to gold catalysis, we reasoned that 5-exo-dig cyclizations onto alkynes, promoted by iodine(III) species, to generate carbonÀcarbon bonds should be feasible. To this end, we prepared alkyne 1a and surveyed hypervalent iodine reagents as mediators for intramolecular cyclization. Upon stirring with PhI(OAc) 2 (PIDA) or PhI(OCOCF 3 ) 2 (PIFA) in acetonitrile at room temperature, or at reflux with PIFA, no reaction took place (Table 1, entries 1 and 2). Stirring with Koser's reagent (PhI(OH)OTs) returned ∼95% of 1a, but some unidentifiable products (at that point) were evident in the 1 H NMR spectrum (entry 3). At this stage, we decided to generate the hypervalent iodine species in situ from iodobenzene with p-toluenesulfonic acid and m-chloroperbenzoic acid, and we were delighted to find that (1) For an excellent review, see: Furstner, A.; Davies, P. W. Angew. Chem., Int. Ed. 2007, 46, 3410-3449. (2) Miyamoto, K.; Sei, Y.; Yamaguchi, K.; Ochiai, M. J. Am. Chem. Soc. 2009, 131, 1382-1383. (3) For a selected example, see: Bi, H.-P.; Guo, L.-N.; Duan, X.-H.; Gou, F.-R.; Huang, S.-H.; Liu, X.-Y.; Liang, Y.-M. Org. Lett. 2007, 9, 397-400. (4) (a) Pardo, L. M.; Tellitu, I.; Domı´nguez, E. Synthesis 2010, 971-978. (b) Tellitu, I.; Serna, S.; Herrero, M. T.; Moreno, I.; Domı´nguez, E.; SanMartin, R. J. Org. Chem. 2007, 72, 1526-1529.(5) For reviews on hypervalent iodine chemistry, see: (a) Zhdankin, V. V.

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In the presence of an oxidant, sodium iodide is converted into hypoiodous acid which effects the rearrangement of tertiary propargylic alcohols to α-iodoenones in good yields.