Stereoselective Synthesis of Bicyclo[4.2.1]nonanes – a Temporary‐Bridge Approach to Cyclooctanoids

Abstract

A series of cis-α,γ-difunctionalized five-membered cyclic β-oxo esters have been chemo-, regio-and diastereoselectively prepared through an efficient domino anionic ring-cleavage/ ring-reconstitution/alkylation sequence including a 1,3-shift of the ester group. These unsaturated substrates were successfully engaged in various ring-closing metatheses to pro-

Construction of Eight-Membered Carbocycles with Trisubstituted Double Bonds Using the Ring Closing Metathesis Reaction

“…Further applications involving cyclization to cycloheptene derivative 4 6 and the ring opening to cyclooctene 47 was realized by Rodriguez ( Scheme 10 ) [ 28 , 29 ]. An interesting review was published by Rodriguez [ 30 ].…”

Syntheses and Applications of Functionalized Bicyclo[3.2.1]octanes: Thirteen Years of Progress

“…The temporary-bridge approach has become a classic for the preparation of medium-sized rings, 256 The retro-Dieckmann-type fragmentation of 8-oxobicyclo[3.2.1]octane derivatives pioneered by Stork and Landesman in 1956 259 has been frequently used for the preparation of seven-membered rings. Some of the recent examples include the fragmentation of substrates 85a−c with formic acid, 51b 98a,b 55 and 137a,b 73a with methanol, and a series of quinone−styrene [5 + 2]-cycloadducts with primary amines.…”

“…The temporary-bridge approach has become a classic for the preparation of medium-sized rings, and bicyclo[3.2.1]octane derivatives have been thoroughly employed for the synthesis of polyfunctionalized cycloheptanes, which are also found in the core structure of many natural products and biologically active molecules. For example, Ramesh and Hassner have described the preparation and then the fragmentation of the tricyclic hemiacetals 463 using Suarez’s oxidative alkoxy radical β-fragmentation to give the seven-membered rings 464a – d in good overall yield, albeit with low regio- and diastereoselectivity (Scheme ) .…”

Application of a metathesis reaction in the synthesis of sterically congested medium-sized rings. A direct ring closing versus a double bond migration–ring closing process

“…The closing of an eight-membered ring was, generally, considered to be a difficult reaction. 1-6 However, some encouraging examples of the application of metathesis in the synthesis of complex cyclooctene derivatives have been reported [7][8][9][10][11][12][13][14][15][16] (more recent related examples are also noteworthy [17][18][19][20] ). The distinctive feature of substrate 3 was the l,l relative configuration around C-2,C-1¢ and C-1¢,C-2¢ as well as the presence of a bulky S-tert-butylthiocarbonyl group in a position adjacent to the cyclopentane ring.…”