Tetrahedron report number 748 Recent advances in the Stevens rearrangement of ammonium ylides. Application to the synthesis of alkaloid natural products John A. Vanecko, a Hayley Wan b and Frederick G. West b, * a Department of Chemistry, University of Utah 315 South 1400 East, Room 2020 Salt Lake City, Utah, UT 84112-0850, USA b Department of Chemistry, University of Alberta, W5-67 Gunning-Lemieux Chemistry Centre, Edmonton, AB T6G 2G2, Canada Received 2 August 2005 Available online 28 October 2005 Contents 1. Introduction .................................................................. 1044 2. Mechanism of the Stevens rearrangement ............................................ 1044 3. Ylide formation ............................................................... 1044 3.1. Base-induced ylide generation ................................................ 1044 3.2. Fluoride-mediated desilylation ............................................... 1044 3.3. Ylide generation via carbenes ................................................ 1044 4. New methodology ............................................................. 1045 4.1. Recent advances in ylide generation methodology ................................. 1045 4.1.1. Intramolecular carbenoid-amine reactions ................................. 1045 4.1.2. Intermolecular carbenoid–amine reactions ................................. 1046 4.1.3. Ylide formation under Mitsunobu conditions ............................... 1047 4.1.4. Selectivity in ylide rearrangements under disilylative conditions ................. 1048 4.1.5. Competing formation of ammonium and carbonyl ylides ...................... 1049 4.1.6. Diastereoselective nitrogen quaternization ................................. 1050 4.1.7. Stevens rearrangement of cyclic hemiacetals ............................... 1050 4.2. Ring expansion methodology ................................................ 1051 4.2.1. Synthesis of 5,7-bicyclic systems ....................................... 1051 4.2.2. Enantiopure morpholines from oxazolidines ................................ 1051 4.2.3. Synthesis of pyrrolidines from enantiomerically pure azetidines ................. 1052 5. Synthetic applications of the Stevens rearrangement of ammonium ylides .................... 1053 5.1. Approaches to isopavines and the morphine core .................................. 1053 5.2. Synthesis of HIV-1 RT inhibitors ............................................. 1054 5.3. Synthesis of azacene ring systems ............................................. 1055 5.4. Synthesis of epilupinine .................................................... 1055 5.5. Synthesis of benzazepine alkaloids ............................................ 1056 5.6. Hydroxylated quinolizidines via silyl-directed [1,2]-shift ............................ 1057 5.7. Synthesis of pyrrolizidine alkaloids turniforcidine and platynecine ..................... 1057 5.8. Approach to indolizidinone alkaloids ........................................... 1058 5.9. Approaches toward pyrrolo[1,2-a]azepine frameworks .............................. 1058 6. Conclusions .................................................................. 1059 References and notes ........................................................... 1059 Biographical sketch ............................................................ 1062 0040–4020/$ - see front matter q 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.tet.2005.09.123 Tetrahedron 62 (2006) 1043–1062 Keywords: Ylide; Amines; Ammonium [1,2]-Shift. * Corresponding author. Tel.: C1 780 492 8187; fax: C1 780 492 8231; e-mail: frederick.west@ualberta.ca