RESUMO
A set of cascade benzannulations of readily accessible chromone-3-carboxaldehydes and γ-nitroaldehydes for synthesizing biologically relevant 2-hydroxybenzophenones has been developed. The cascade was found to provide a transition-metal-free strategy for synthesizing 2-hydroxybenzophenones in acceptable yields (up to 57%).
Assuntos
BenzofenonasRESUMO
A novel methodology toward the diversity-oriented asymmetric construction of densely functionalized isoxazole-dispirobisoxindoles was developed. This approach is distinguished by an organocatalytic stereo- and appealing ß-regioselective [3 + 2] cycloaddition reaction of 3-methyl-4-nitro-5-isatylidenyl-isoxazoles and 3-isothiocyanato oxindoles. Complex polycyclic oxindoles 3 featuring two different oxindole moieties and three contiguous stereocenters were smoothly afforded in up to 96% yield, 96% ee, and >20 : 1 dr. The described method, which is different from our previous work of α-regioselective asymmetric annulation of 3-methyl-4-nitro-5-isatylidenyl-isoxazoles, is the first ß-regioselective asymmetric annulation.
RESUMO
Described herein is the development of a facile and efficient methodology for the synthesis of novel turmerone motif-fused 3,3'-pyrrolidinyl-dispirooxindoles 3-5 via a multicomponent 1,3-dipolar cycloaddition of dienones 2 with azomethine ylides (thermally generated in situfrom isatins and proline or thioproline or sarcosine). Products bearing four or three consecutive stereocenters consist of two oxindole moieties and a pyrrolidinyl core, including vicinal spiroquaternary stereocenters fused in one ring structure were smoothly obtained in high yields (up to 93% yield) with good diastereoselectivity (up to >20:1). Another valuable application of this method was for the design of new hybrid architectures for biological screening through the adequate fusion of these sub-units of turmerone and 3,3'-pyrrolidinyl-dispirooxindole, generating drug-like molecules.
