A Ni-catalyzed benzannulation reaction of cyclobutenones and alkynes provides a rapid synthesis of heavily substituted phenols. The regioselectivity of this reaction can be modulated by variation of substituents on the alkyne. Though the incorporation of Lewis basic donors provides modest selectivities, the use of aryl substituents can provide high levels of regiocontrol. Finally, alkynylboronates derived from alkyl-substituted acetylenes provide both high yields and regioselectivities. This study suggests that alkynes bearing one sp(2) - and one sp(3) -based substituent can undergo benzannulation with high levels of regiocontrol whereby the sp(3) -based group is incorporated ortho-to the phenolic OH.
The E/Z-selectivity in the formation of silylketene acetals derived from phenylacetate esters, mediated by LiHMDS, has been studied by in situ NMR techniques. The formation is seen to be highly E-selective with use of the newly developed protocol. Isolated aryl-substituted silylketene acetals are now attainable with high levels of E-geometrical purity in excellent yield.
α-Alkyl β-amino esters are available in high diastereoselectivity through a silicon-free Claisen enolate [3,3]-sigmatropic rearrangement of enamide esters. Optimisation studies have probed the crucial role of the initial enolisation and the nature of the enamide N-centre. The demonstration of chirality transfer and the formation of β-proline systems, is also presented.
Meeting Summary
The 20th annual symposium of the International Isotope Society's United Kingdom Group took place at the Wellcome Genome Campus, Hinxton, Cambridge, UK on Tuesday 18 October 2011. The meeting was attended by around 70 delegates from academia and industry, the life sciences, chemical, radiochemical and scientific instrument suppliers.
Delegates were welcomed by Dr Ken Lawrie (GlaxoSmithKline, UK, chair of the IIS UK group). The subsequent scientific programme consisted of oral and poster presentations on isotopic chemistry and applications of labelled compounds or of chemistry with potential implications for isotopic synthesis. Both short‐lived and long‐lived isotopes were represented, as were stable isotopes. The symposium programme was divided into a morning session chaired by Prof. Chris Willis (University of Bristol, UK) and afternoon sessions chaired by Mr Mike Chappelle (Quotient Biosciences, UK) and by Dr Nick Bushby (AstraZeneca, UK). The UK meeting concluded with remarks from Dr Ken Lawrie (GlaxoSmithKline, Stevenage, UK).
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