Three/Four/Five‐Component Diastereoselective Cyclization of Fischer Carbene Complexes, Lithium Enolates, and Allylmagnesium Bromide

Abstract

From three simple starting materials, the diastereoselective synthesis of pentasubstituted cyclopentanols or tetrasubstituted cyclohexane‐1,4‐diols can be controlled by the appropriate choice of lithium enolate (see scheme). The overall one‐pot transformation leads to the formation of up to five new CC bonds and up to four contiguous stereogenic centers.

Reactions of Allylmagnesium Reagents with Carbonyl Compounds and Compounds with C═N Double Bonds: Their Diastereoselectivities Generally Cannot Be Analyzed Using the Felkin–Anh and Chelation-Control Models

“…A case of β-chelation controlled addition was reported in the context of a chromium-mediated transformation (Scheme ). This reaction incorporates the allyl fragment into the ring by an addition reaction onto β-alkoxy-substituted ketone 122 . The product of that step, alkoxide 123 , was attributed by the authors to be formed through the chelated transition state 126 , where the nucleophile was delivered to the external face of carbonyl group, which faces away from the ring.…”

Group 6 Fischer carbene complexes: “chemical multitalents” for multi-component reactions

“…Both processes involve the generation of acyl chromate species through sequential addition of a ketone or ester lithium enolate 259/260 and allyl magnesium bromide to chromium carbene complexes 1c (Scheme 45) [79].…”

Bis(trimethylsilyl)ketene acetals as 1,3-dinucleophiles. Formation of an anhydride from (pentacarbonyl)(phenylethoxy)tungstacarbene

“…This result can be rationalized in view of previous observations from this Laboratory [11,12] and from others [13,14]. The addition of nucleophiles to Fischer carbene complexes to give useful functionalized tetrahedral intermediates is now well established: addition of the enolate 4 originating from the ketene acetal and potassium t-butoxide probably led to a potassium (1-alkoxy 3-oxatrimethylsilylcarboxylate)pentacarbonyl tungstate (5).…”