Publications by authors named "Euan A Arnott"

2 Publications

  • Page 1 of 1

POCl3 chlorination of 4-quinazolones.

J Org Chem 2011 Mar 4;76(6):1653-61. Epub 2011 Feb 4.

AstraZeneca, Pharmaceutical Development, Silk Road Business Park, Charter Way, Macclesfield, Cheshire SK10 2NA, UK.

The reaction of quinazolones with POCl(3) to form the corresponding chloroquinazolines occurs in two distinct stages, which can be separated through appropriate temperature control. An initial phosphorylation reaction occurs readily under basic conditions (R(3)N, aq pK(a) > 9) at t < 25 °C to give a variety of phosphorylated intermediates. Pseudodimer formation, arising from reaction between phosphorylated intermediates and unreacted quinazolone, is completely suppressed at these temperatures, provided the system remains basic throughout the POCl(3)addition. Clean turnover of phosphorylated quinazolones to the corresponding chloroquinazoline is then achieved by heating to 70-90 °C. (N)- and (O)-phosphorylated intermediates, involving multiple substitution at phosphorus, have been identified and their reactions monitored using a combination of (1)H, (31)P, and (19)F NMR. Kinetic analysis of the reaction profiles suggest that the various intermediates react with both Cl(-) and Cl(2)P(O)O(-), but product formation arises exclusively from reaction of (O)-phosphorylated intermediates with Cl(-). (O)- and (N)-phosphorylated intermediates equilibrate rapidly on the time scale of the reaction. A minimum of 1 molar equiv of POCl(3) is required for efficient conversion of the intermediates to product.
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http://dx.doi.org/10.1021/jo102262kDOI Listing
March 2011

Remote stereocontrol using allylstannanes: reversal in stereoselectivity using indium(III) and bismuth(III) halides as promoters.

Chem Commun (Camb) 2003 Jun(12):1460-1

Department of Chemistry, The University of Manchester, Oxford Road, Manchester, UK M13 9PL.

Allyl-indium(III) and -bismuth(III) dihalides, generated by transmetallation of 5-benzyloxy-4-methylpent-2-enyl(tributyl)stannane 1, react with aldehydes with useful levels of 1,5-stereocontrol, a 93:7 ratio of 1,5-epimers in favour of the 1,5-anti-(E)-stereoisomers 7 and 11 typically being obtained using bismuth(III) iodide. The 4-benzyloxypent-2-enylstannane 4 similarly gives the 1,5-syn-(E)-hex-3-enols 13 also with ca. 93:7, stereoselectivity.
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http://dx.doi.org/10.1039/b303151aDOI Listing
June 2003