TY - JOUR
T1 - Highly regio- and Stereoselective Diels–Alder Cycloadditions of α-Alkoxyvinyl(ethoxy)carbene complexes with exo-heterocyclic dienes
AU - Feliciano, Alberto
AU - Flores-Conde, M. Inés
AU - Padilla, Rosa
AU - Espinoza-Hicks, Carlos
AU - Camacho-Dávila, Alejandro
AU - Rentería, Marvin
AU - Vázquez, Miguel Angel
AU - Tamariz, Joaquín
AU - Delgado, Francisco
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2018/11/15
Y1 - 2018/11/15
N2 - A comparative study of reactivity and selectivity was carried out between the α-alkoxyvinyl(ethoxy)carbene complexes of group 6 metals (CO)5M = C[C(=CH2)(OR)]OEt [1a–c: M = Cr; 6a–c: M = Mo; 7a–c: M = W; a, R = Et; b, R = n–Pr; c, R = n–Bu] and exo-heterocyclic dienes 5a–e in Diels–Alder reactions. The cycloadditions of complexes 1, 6 and 7 with the unsubstituted diene 5a (R1 = H) were performed at 25 °C, proving to be highly regioselective in favor of the para pentacarbonyl cycloadducts 8, 10 and 12. On the other hand, the cycloadditions of complexes 1a–c and 6a–c with the substituted dienes 5b–e (R1 = Me or Et) took place at a higher temperature (50 °C) to afford the novel para-endo C,O-chelated tetracarbonyl cycloadducts 15a–f and 17a–d, respectively, in high regio- and stereoselectivity. DFT calculations of the transition states rationalized their selectivity. Under the same reaction conditions, the W(0) carbene complexes 7a–c produced the para-endo non-chelated pentacarbonyl complex adducts 19a–e. The stereochemical assignment of the cycloadducts was supported by NOE measurements. The C,O-chelated tetracarbonyl cycloadduct 15b and non-chelated cycloadduct 19d were further characterized by single-crystal X-ray diffraction.
AB - A comparative study of reactivity and selectivity was carried out between the α-alkoxyvinyl(ethoxy)carbene complexes of group 6 metals (CO)5M = C[C(=CH2)(OR)]OEt [1a–c: M = Cr; 6a–c: M = Mo; 7a–c: M = W; a, R = Et; b, R = n–Pr; c, R = n–Bu] and exo-heterocyclic dienes 5a–e in Diels–Alder reactions. The cycloadditions of complexes 1, 6 and 7 with the unsubstituted diene 5a (R1 = H) were performed at 25 °C, proving to be highly regioselective in favor of the para pentacarbonyl cycloadducts 8, 10 and 12. On the other hand, the cycloadditions of complexes 1a–c and 6a–c with the substituted dienes 5b–e (R1 = Me or Et) took place at a higher temperature (50 °C) to afford the novel para-endo C,O-chelated tetracarbonyl cycloadducts 15a–f and 17a–d, respectively, in high regio- and stereoselectivity. DFT calculations of the transition states rationalized their selectivity. Under the same reaction conditions, the W(0) carbene complexes 7a–c produced the para-endo non-chelated pentacarbonyl complex adducts 19a–e. The stereochemical assignment of the cycloadducts was supported by NOE measurements. The C,O-chelated tetracarbonyl cycloadduct 15b and non-chelated cycloadduct 19d were further characterized by single-crystal X-ray diffraction.
KW - (α-alkoxyvinyl)carbene complexes
KW - Diels-Alder
KW - Pentacarbonyl and C,O-chelated tetracarbonyl cycloadducts
KW - Regioselective and stereoselective cycloaddition
UR - http://www.scopus.com/inward/record.url?scp=85053314747&partnerID=8YFLogxK
U2 - 10.1016/j.jorganchem.2018.08.024
DO - 10.1016/j.jorganchem.2018.08.024
M3 - Artículo
SN - 0022-328X
VL - 875
SP - 59
EP - 71
JO - Journal of Organometallic Chemistry
JF - Journal of Organometallic Chemistry
ER -