Synthesis of 2-Imino-1,3,4-thiadiazoles from Hydrazides and Isothiocyanates via Sequential Oxidation and P(NMe<sub>2</sub>)<sub>3</sub>-Mediated Annulation Reactions
N-acyldiazenes with isothiocyanates, producing 2-imino-1,3,4-thiadiazoles, is reported. This reaction proceeds well with crude N-acyldiazenes derived from the oxidation of hydrazides by iodine and permits the sequential synthesis of products directly from hydrazides without purification of the less stable N-acyldiazene intermediates. The reaction does not require transition metals and is a simple, scalable operation
A facile N-heterocyclic carbene catalytic enantioselective aza-Diels–Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study showed that cis-TSa, formed from a top face approach of oxodiazene to cis-IIa, is the most favorable transition state and is consistent with the experimental
(PBu3)-promoted annulation reaction at room temperature. In this synthetic process, crude less stable N-aroyldiazene intermediates generated by I2-mediated oxidation of hydrazides were used directly in a subsequent annulation reaction to afford the selenadiazole products. The merits of the present synthetic strategy also include absence of transition metals and gram-scale synthesis.
2-亚氨基-1,3,4-硒二唑衍生物可以在室温下通过连续氧化和三丁基膦 (PBu 3 ) 促进的环化反应从酰肼和异硒氰酸酯合成。在该合成过程中,由 I 2 -介导的酰肼氧化产生的较不稳定的粗N-芳酰基二氮中间体直接用于随后的环化反应,以提供硒二唑产物。本合成策略的优点还包括没有过渡金属和克级合成。
Organocatalytic enantioselective [2 + 4]-annulation of γ-substituted allenoates with <i>N</i>-acyldiazenes for the synthesis of optically active 1,3,4-oxadiazines
作者:Xing Guo、Xuling Chen、Yuyu Cheng、Xiaoyong Chang、Xuechen Li、Pengfei Li
DOI:10.1039/d0ob02508a
日期:——
An enantioselective [2 + 4]-annulation of γ-substituted allenoates with N-acyldiazenes has been developed for the first time. In the presence of an L-proline-derived DMAP analogue, the annulation proceeded smoothly to afford a broad range of 1,3,4-oxadiazine derivatives in good to excellent yields with high stereoselectivities.
[4+2] Cycloaddition of Ketenes with<i>N</i>-Benzoyldiazenes Catalyzed by N-Heterocyclic Carbenes
作者:Xue-Liang Huang、Lin He、Pan-Lin Shao、Song Ye
DOI:10.1002/anie.200804487
日期:2009.1
Enantioselectivity switch: A catalytic enantioselective [4+2] cycloaddition reaction of alkylarylketenes with N‐aryl‐N′‐benzoyldiazenes or N,N′‐dibenzoyldiazenes to give 1,3,4‐oxadiazin‐6‐ones 1 was developed by employing N‐heterocyclic carbene (NHC) catalysts. The enantioselectivities could be switched for most reactions by changing the substituents on the NHC catalyst. TBS=tert‐butyldimethylsilyl