Propionyl imides

R—C—N-C-R II II II OHO Imide CH3CO—NH—OCCH2CH3 Acetyl propionyl imide -ic or -oic acid to -imide... 

P, P] Tin(II) enolates of propionyl imides do not undergo uncatalyzed reactions with enones. Lewis acid catalysis results in the construction of 1,4-addition products. The stereoselectivity of this reaction has been examined by Mukaiyama and co-workers (87,88) and is summarized in Scheme 41 and Table 14. The tin(II) enolates were generated by the action of tin(II) triflate with N-ethylpiperidine on the propionyl imide. Although not examined, it is likely that this procedure results in the generation of a Z enolate (89). A process can be envisioned whereby transmetallation occurs to yield a silyl ether and a tin(II) species capable of Lewis acidic behavior. Hence, either direct conjugate addition of the tin enolate to a silyl-activated acceptor or transmetallation to... 

Addition ofTin Enolates of Propionyl Imides to a,/J-Unsaturated Ketones (Scheme 41) Enone... 

Propioloyl chloride, 1065 t Propionyl chloride, 1163 Sebacoyl chloride, 3341 Sulflnyl chloride, 4096 Sulfonyl chloride, 4099 Sulfm oxide-(iV-fluorosulfonyl)imide, 4305 Sulfuryl azide chloride, 4031 Terephthaloyl chloride, 2880... 

From the illustrated (S)-valinol imide (175), the derived dibutylboryl enolates undergo condensation with a broad range of aldehydes in greater than 99% asymmetric induction for both newly formed asymmetric centers 180). Evans et al. have shown that the propionyl sidely chain in (175) may be replaced by other alkanoyl substituents without loss of stereoselectivity in the aldol type reaction 180). 

In 1995, Boeckman et al. disclosed a highly diastereoselective aldol reaction using the ligand 79 derived from chiral bicyclic lactam28 (Scheme 2.1z). The imide 80, readily prepared from bicyclic lactam 79 and propionyl chloride, was converted to the boron Z-enolate, which was then treated with a representative series of aldehydes at -40° C for 48 hours. The levels of diastereoselectivity observed in reactions of boron enolate derived from 80 are comparable to those... 

Tetrafluoropropionamide added in small portions to a suspension of PCI5 in benzene which is then evaporated under a stream of N2 N-(tetrafluoro-propionyl) trichlorophosphine imide. Y 73%. D. G. England, R. V. Lindsey, and L. R. Melby, Am. Soc. 80, 6442 (1958). 

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