A Stereoselective Carbocyclization of Bis(allenes) with Germylstannane Catalyzed by Palladium Complexes

Abstract

Diastereoselective germastannylation of bis(allenes) with germylstannanes, catalyzed by palladium complexes, for the construction of cis or trans five‐membered cyclic systems has been investigated. We observed that the relative stereochemical arrangements of the reaction products depends on the substituents in the reagents containing Ge−Sn σ‐bonds. When the reagent Ph3GeSnBu3 was employed in the Pd0‐catalyzed carbocyclization of bis(allenes), trans‐cyclized products and/or cis‐fused bicyclic dienes were produced. In contrast, cis cyclic compounds were obtained, again along with cis‐fused bicyclic dienes, from the reaction with Bu3GeSnBu3. NMR experiments to establish the stereochemical relationships and a mechanistic speculation for this transformation as a possible explanation for the different stereochemical outcomes are also described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

Catalytic bismetallative multicomponent coupling reactions: scope, applications, and mechanisms

“…19 They pointed out that the stereochemistry of the outcomes is dependent on the Ge – Sn reagents and the catalysts that are used in the reactions. Bis(allene) 32 can react with Ph 3 Ge–SnBu 3 ( 43 ) with a catalytic amount of (π-allyl) 2 Pd 2 Cl 2 (5 mol %) to afford the trans -cyclized product 44 (77% yield).…”

“…For allene-allene coupling, Ge-Sn reagents can also participate as a coupling component; this process was investigated by Yu et al (Scheme 16). 19 They pointed out that the stereochemistry of the outcomes is dependent on the Ge-Sn reagents and the catalysts that are used in the reactions. Bis(allene) 32 can react with Ph 3 Ge-SnBu 3 (43) with a catalytic amount of (p-allyl) 2 -Pd 2 Cl 2 (5 mol%) to afford the trans-cyclized product 44 (77% yield).…”

A Rh(I)‐Catalyzed Cascade Cyclization of 1,5‐Bisallenes and Alkynes for the Formation of cis‐3,4‐Arylvinyl Pyrrolidines and Cyclopentanes

“…Here again, the size of the ring formed upon carbometallation depends on the catalytic system used. Processes in which the two inner bonds of the two allenes forge 5-membered rings have been described under palladium catalysis by Kang et al, [25] Yu et al [26] and Ma et al, [27][28] (Scheme 1c) under platinum catalysis by Jang et al, [29] and under nickel catalysis by Arai et al [30] Conversely, cyclizations involving the two external double bonds, thus affording 7-membered scaffolds, have been reported by Bäckvall et al [31][32] under palladium catalysis (Scheme 1c) and by Muñoz et al [33] under platinum catalysis. Ma et al, [34] using a reaction manifold that does not directly react the two allenes, also obtained 10membered macrocycles.…”

Cyclization reactions of bis(allenes) for the synthesis of polycarbo(hetero)cycles

“…Analogously, similar Pd-catalyzed cyclizations of 1,5-bis(allenes) with germylstannanes have been accomplished under the conditions described above. 47 Thus, when Y group was Bu 3 Ge, cis products 142 were obtained in 41−51% yields, while with Y being Ph 3 Ge group, trans 35 products 143 were formed in 61−77% yields. In addition, in some cases, when the reaction time was prolonged to 12 hours, cis-fused bicyclic dienes 144 were isolated in low yield, formed via [2+2] cycloaddition of both terminal double bonds of the bis(allene) (Scheme 52).…”