Regioselective rhodium-catalyzed allylic linchpin cross-coupling reactions: diastereospecific construction of anti-1,3-carbon stereogenic centers and C(2)-symmetrical fragments.
Regioselective rhodium-catalyzed allylic linchpin cross-coupling reactions: diastereospecific construction of anti-1,3-carbon stereogenic centers and C(2)-symmetrical fragments.
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DOI：
10.1021/ja005689m
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发表时间：
2001-02
影响因子：
15
通讯作者：
Evans Pa;Kennedy Lj
中科院分区：
文献类型：
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作者：
Evans Pa;Kennedy Lj
The stereocontrolled construction of acyclic anti-1, 3-carbon stereogenic centers, including C2-symmetrical fragments, represents a fundamentally important process for target-directed synthesis. 1 Although a variety of excellent synthetic strategies have been devised to address this problem, the ability to control 1, 3-carbon stereogenic centers by using sequential enantiospecific metal-catalyzed allylic substitution reactions with unsymmetrical acyclic chiral nonracemic secondary allylic alcohol derivatives has not been addressed (eq 1). 2 The metal-catalyzed allylic substitution with R-substituted malonates has been examined; however, symmetrical or stereoelectronically biased substrates are required to circumvent poor regioselectivity. 3, 4We envisioned that the rhodium-catalyzed allylic substitution reaction would facilitate this type of linchpin cross-coupling reaction owing to its propensity to undergo selective alkylation through the formation of a distorted π-allyl or enyl (σ+ π) organorhodium intermediate. 5-7 Herein, we now describe the sequential regioselective and enantiospecific rhodium-catalyzed allylic alkylation of unsymmetrical acyclic chiral nonracemic allylic carbonates i and iii with the sodium salt of dimethyl malonate ii for the construction of acyclic anti-and C2-symmetrical 1, 3-carbon stereogenic centers iv (eq 1, R1* R2 and R1) R2).
