M. Bilodeau. d.A. evans A Survey of Soft Enolization Techniques Chem 115 Tin enolates Titanium enolates N-ethylpiperidine i-PrCHO The Early Literature Lehnert, W. Tetrahedron Lett. 1970, 4723-4724 Diamines mE DA 65% wield. 9. sy atits TiCl4 Evans. Weber J. Am. Chem. Soc. 1986. 108 6757 THF 75% yie N-ethylpiperidine +PICHO Harrison. C. R. Tetrahedron Lett 1987. 28. 4135-4138 Evans, Clark, Metternich, Novack, Sheppard J. Am. Chem. Soc. 1990, 112, 866 Ketone and aldehyde combined followed by sequential addn of TiCl and then amine 2. i-PrCHO Brocchini. Eberle. Lawton J. Am. Chem. Soc. 1988. 110. 5211-5212 Evans, Sheppard J. Org. Chem. 1990, 55, 5192 人人 0-15:1Z 22A-06 Ketone Acidity 11/1/01 3: 42 PMThe Early Literature 10-15:1 Z/E TiCl4 DIPEA THF -40° C ■ Brocchini, Eberle, Lawton J. Am. Chem. Soc. 1988, 110, 5211-5212. 91% yield 95:5 syn/anti TiCl4 Et3N CH2Cl2, 0° C 30 min + PhCHO Ketone and aldehyde combined followed by sequential addn of TiCl4 and then amine ■ Harrison, C. R. Tetrahedron Lett. 1987, 28, 4135-4138. 75% yield TiCl4 Pyridine THF Titanium Enolates ■ Lehnert, W. Tetrahedron Lett. 1970, 4723-4724. No diamine: 60% yield, 61:39 syn/anti Diamine= TMEDA, 65% yield, 9:91 anti/syn i-PrCHO Sn(OTf)2 N-ethylpiperidine [Diamine] Evans, Clark, Metternich, Novack, Sheppard J. Am. Chem. Soc. 1990, 112, 866. 1. Sn(OTf)2 Et3N 2. i-PrCHO Evans, Weber J. Am. Chem. Soc. 1986, 108, 6757. i-PrCHO Sn(OTf)2 N-ethylpiperidine CH2Cl2, -78° C Tin Enolates M. Bilodeau, D.A. Evans A Survey of 'Soft' Enolization Techniques Chem 115 79% Diastereoselection >95:5 Sn(OTf)2 Et3N Evans, Sheppard J. Org. Chem. 1990, 55, 5192. O N O O NCS Bn Bn O N O O Me O Me Me O O N O Bn HN O N O O O O H Me Me O Bn Me Me Me OH S N S OBn O O N S S Me BnO Me OH Et Et O EtO OEt O O O EtO OEt O Et Et Ph Me O Ph Ph O Me OH NO2 O S OH CHO N S O NO2 OH O Me OH Me Me H O Me Me Me O CH2 Me XP O O Me CH2 O O O O Me O Me Me Me Me Bn O Me 22A-06 Ketone Acidity 11/1/01 3:42 PM