Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login to access the full content or check if you have access via
1.1.1.2.1 Starting from Dialdehydes

DOI: 10.1055/sos-SD-204-00001

Wang, X. -W.; Wang, Y.; Jia, J.Science of Synthesis: Asymmetric Organocatalysis, (2012123.

Although amine-catalyzed nonasymmetric enolexo aldolizations are relatively common, and catalytic asymmetric enolendo aldolizations have been known since the 1980s (see Section 1.1.1.1), the first catalytic asymmetric enolexo aldolizations were not developed until 2003, when a highly enantioselective 6-enolexo aldolization of dicarbonyl compounds was established.[‌98‌] Treatment of a variety of achiral dials 71 with a catalytic amount (10mol%) of (S)-proline [(S)-2] smoothly gives the corresponding cyclic anti-aldols 72 in good to high yields and excellent stereoselectivity (Table 1). However, a single substituent in the 4-position, as in dial 73, has an unfavorable effect on the stereoselectivity of the cycloaldolization, leading to the formation of all four possible diastereomeric aldols 74 in a 22:5:5:1 ratio. The substrate scope is not limited to dials: keto aldehydes can also be used in this reaction, as shown by the case of keto aldehyde 75. This anti-diastereoselective reaction complements alternative methods, such as the highly enantioselective and syn-diastereoselective reduction of β-keto esters by bakerʼs yeast.[‌99‌,‌100‌]

Meeee 8 (M)-Meeeeee-Meeeeeeee Meeeeeeeeeeeeeee 8-Meeeeee Meeeeeeeeeeee ee Meeeeeeeee Meeeeeeee[‌88‌]

Meeeeeee Meeeeeee Meeeeee Meeeee (%) ee (%) ee (%) Mee
88 88:8 88 [‌88‌]
88 >88:8 88 [‌88‌]
88 >88:8 88 [‌88‌]
88 88:8:8:8 88, 88, 88, 8 [‌88‌]
88 8:8 88 [‌88‌]
88 8:8 88 [‌88‌]

e Meeee ee eee eeeeeeeeeeeee eeee eeeee eeeeeeeee ee eeee eeee MeMM8.

Meeeeee eeeeeee eeeeeeeeeeeee eeeeeeeee ee eeeeeeeeeeeee eeeeee eeeee eeee eeeee eeeeeeeeeeee eeeeeeee, eee eeeeeeeeeeeee eeeeeee-eeeeeeeee eeeeeee eeeeeeeeeee eeeee eee eeeeeeeeeeeee eeeee eeeeeeee eeeeeeee. Me eeeeeeeeee eeee 8-eeeeeee eeeeeeeeeeeee eeeeeeeee ee eeeeeee (Meeee 8),[‌88‌] eee eeeeeeeeeeeee 8-eeeeeee eeeeeeeeeeeee eee eeee eeeeeeeeeeeeeee. Mee eeeeeee, eeeeeeeee ee eeeeeeeeee (88) eeee e eeeeeeeee eeeeee ee (M)-eeeeeee [(M)-8] eeeee eee eeeeeeeeeeeee eeeee eeeeeeee 88 eee 88 eeee eeee eeeeee eeeeeeeee- eee eeeeeeeeeeeeeeeeee (Meeeee 88).[‌88‌]

Meeeee 88 (M)-Meeeeee-Meeeeeeee 8-Meeeeee Meeeeeeeeeee ee Meeeeeeeee[‌88‌]

Meeeeee-eeeeeeeee 8-eeeeeee eeeeeeeeeeee eee ee eeee ee eee eeeeeeeeeeeeeeee ee e eeee-eeeeeeeeee 88 ee e eeeee eeeeeeeee ee (+)-eeeeeee (88) (Meeeee 88).[‌888‌] M 8:8 eeeeeee ee eee eeeeeeee eeeee eeeeeeee 88, ee eeeeeeeee eeeeeeeeeeee ee eeeeeee, ee eeeeeeee ee 88% eeeee eeee 88eee% (M)-eeeeeee [(M)-8] ee eeee ee eeeeeeee eee eee eeeeeeeeeeee ee eeee-eeeeeeeeee 88 ee eeeeeee ee 88°M. Meeee eeeeeee eeeee, (+)-eeeeeee (88) ee eeeeeeee ee 88% ee.

Meeeee 88 Meeeeee-Meeeeeeee Meeeeeeeeeeeeeee ee e eeee-Meeeeeeeee ee e Meeee Meeeeeeee ee (+)-Meeeeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

eeeee-8-Meeeeeeeeeeeeeeeeeeeeeeeeeeeeee 88; Meeeeee Meeeeeeee:[‌88‌]

Meeeeeeeee eeeeeeee eeeeeeee 88 (8eeee) eee eeeeeeeee ee eee MM8Me8 (88eM) eee eeeeeee eeee (M)- ee (M)-eeeeeee (8; 88ee, 8.8eeee, 8.8 eeeee). Mee eeeeeee eee eeeeeee ee ee eeeee eee eeeeeeee eeeeeeee eeeeeeeeeee (888e). Meeeeeee eeeeeeee 88 eeeee ee eeeeeeee ee eeeeeeee eeeeeee eeeeee, eeee eeee eeeeeeee eeee eeeeeeee eeeeeee ee ee eee eeee eeeeeeeee eeeeeeeee eeee eeeeee eeeee ee ee eeee eeeeeeeee eeee MeMM8, eeeeeeee ee eeeeeee eeeeee.

References


Cookie-Einstellungen