Stereoselective Construction of Eight-Membered Carbocycles by Brook Rearrangement-Mediated [3 + 4] Annulation

Abstract

[reaction: see text] A newly developed strategy for eight-membered carbocycles via [3 + 4] annulation that involves the combination of beta-substituted acryloylsilanes and enolates of cycloheptenone is described. A unique feature of this annulative approach is its capacity to generate, in two steps, eight-membered ring systems containing useful functionalities for further synthetic elaboration from readily available three- and four-carbon components.

Diastereoselective Brook Rearrangement-Mediated [3 + 4] Annulation: Application to a Formal Synthesis of (+)-Laurallene

“…As part of our ongoing program on the development of new synthetic reactions featuring a tandem carbon−carbon bond formation, we have recently reported a Brook rearrangement-mediated [3 + 4] annulation methodology for the construction of eight-membered oxacycles. – In this paper, we report a formal synthesis of (+)-laurallene carried out to show the synthetic utility of the methodology. The target molecule is the Crimmins’ intermediate ( 2 ), which has been converted by Crimmins and co-workers into laurallene ( 1 ) and prelaureatin, the biogenetic precursor of several members of the laurenan structural subclass including 1 (Figure ).…”

Diastereoselective Total Synthesis of (±)‐Schindilactone A, Part 3: The Final Phase and Completion

“…Initially, we worked on the synthesis of compound 12 by route A. Cycloheptenone 18 was treated with LiHMDS and the enolate product [9] was reacted with ethyl 2-bromoacetate to give ketoester 19 in 80 % yield. Grignard reaction of compound 19 with but-3-en-1-ylmagnesium bromide at À20 8C and subsequent lactonization of the alkoxide provided lactone 20 in 73 % yield.…”

Domino Synthesis of Carbo- and Heterocycles Involving a 1,3 or 1,4 C→O Silyl Migration

“…[21][22][23][24][25][26] If a dienolate is the nucleophile, seven-membered rings are formed. [27][28][29][30][31][32] In case of appropriately arranged double bonds, a Cope rearrangement may follow to give eight-membered carbocycles 33 or oxygen heterocycles. 34 In the presence of a primary amine, pyrroles are formed.…”