Synthesis of spiro-cyclics via ring-closing metathesis

Abstract

Various spiro-cyclic systems were synthesized by utilizing ring-closing metathesis as a key step. The required dialkylated starting materials were prepared from various 1,3-diketones or substrates containing an active methylene group.

Synthetic and biological studies on the spiro-mamakone system

“…7,8 Thus, the spiro-acetal linkage between 1,8-dihydroxynaphthalene and an appropriate ketone was to be generated. The known spiro [4.4]nonadione, 3, 9 was chosen as the precursor as it has the appropriate C 9 skeleton and contains orthogonal functionality in each ring. The synthesis of 3 was undertaken, with minor changes to the original literature protocol (Scheme 1).…”

Diversity-Oriented Approach to Macrocyclic Cyclophane Derivatives by Suzuki–Miyaura Cross-Coupling and Olefin Metathesis as Key Steps

“…Various attempts to dibenzylate 1,3-indanedione ( 6 ) were unsuccessful under NaH/THF conditions. On the basis of our earlier experience, 1,3-indanedione ( 6 ) was successfully dialkylated using freshly prepared KF-Celite in one step. , Thus, the 1,3-indanedione ( 6 ) was treated with 2.2 equiv of bromobenzyl bromide in dry acetonitrile under KF-Celite conditions to generate the required dibenzylated products 21a – b in good yields. Along similar lines, allylation was achieved by SM cross-coupling reaction with excess of allylboronic acid pinacol ester under CsF and Pd(PPh 3 ) 4 in dry THF reflux conditions to deliver the required diallyl derivatives 22a – b in good yield.…”

Total syntheses of natural products containing spirocarbocycles

“…Kotha et al have comprehensively reviewed the synthesis of spirocyclics by ring-closing metathesis in 2003. 108…”