Barluenga José, Vicente Rubén, López Luis A, Tomas Miguel
Instituto Universitario de Química Organometalica Enrique Moles, Unidad Asociada al CSIC, Universidad de Oviedo, Julian Clavería 8, 33071 Oviedo, Spain.
J Am Chem Soc. 2006 May 31;128(21):7050-4. doi: 10.1021/ja0586788.
A broad range of functionalized 5-alkylidenecyclopentene derivatives are synthesized by the rhodium(I)-catalyzed [3+2]-cyclization reaction of chromium alkenyl(methoxy)carbene complexes 1 and activated allenes. Thus, amidocyclopentenes 4a-n are readily available from N-allenylamides 2a-c, while phenoxyallene 2e gives access to phenoxycyclopentenes 6. In turn, the cyclization reaction with (alkoxycarbonyl)allenes 3 leads to (alkoxycarbonyl)methylidenecyclopentenes 7-10. In terms of selectivity, most cyclization reactions take place with complete chemo-, regio-, and diastereoselectivity. Representative cycloadducts are efficiently hydrolyzed to the corresponding 2-alkylidenecyclopentanones 11a-e without tautomerization or isomerization. Finally, a tentative reaction pathway is proposed that involves the rhodium(I) carbene complexes as the species responsible for the [3+2]-cyclization.
通过铑（I）催化的铬烯基（甲氧基）卡宾配合物1与活化丙二烯的[3 + 2]环化反应，合成了多种功能化的5-亚烷基环戊烯衍生物。因此，酰胺基环戊烯4a - n可容易地由N-烯丙基酰胺2a - c制得，而苯氧基丙二烯2e可得到苯氧基环戊烯6。反过来，与（烷氧羰基）丙二烯3的环化反应则生成（烷氧羰基）亚甲基环戊烯7 - 10。就选择性而言，大多数环化反应都具有完全的化学、区域和非对映选择性。代表性的环加成产物能有效地水解为相应的2-亚烷基环戊酮11a - e，而不会发生互变异构或异构化。最后，提出了一个初步的反应途径，该途径涉及铑（I）卡宾配合物作为负责[3 + 2]环化的物种。
