The stereochemical outcome of the Lewis acid-mediated glycolate addition of the titanium enolates from protected N-hydroxyacetyl-4-isopropyl-1,3-thiazolidine-2-thiones to dimethyl and dibenzyl acetals depends on the hydroxyl protecting group. Particularly, the pivaloyl protected glycolate derivative provides the reluctant anti adducts in high yields and diastereomeric ratios, which can be isolated and further converted in enantiomerically pure form to β-methoxy or β-benzyloxy α-pivaloyloxy carbonyl fragments in a straightforward manner.

The title compounds are prepared by Parov reaction of cyclopentadiene, anilines, and benzaldehydes.

Diastereoselective Additions of Titanium Enolates from N-Glycolyl Thiazolidinethiones to Acetals. -The stereoselective outcome of the title reaction is found to depend on the nature of the O-protecting group of glycolate substrate. With pivaloyl protected educts high anti-selectivity can be achieved. The products can smoothly be converted into diverse optically active α,β-dialkoxylated carbonyl compounds such as (VII), which are useful synthetic synthons. -(BAIGET, J.; CABA, M.; GALVEZ, E.; ROMEA*, P.; URPI, F.; FONT-BARDIA, M.; J.

Die Pyrolyse (650°) von 1‐Phenylpyrrol‐2,3‐dicarbonsäureanhydrid (I) unter einer Stickstoffatmosphäre von 12 Torr liefert die Phenylpyrrole (III)‐(VII).