Abnormal Condensation of Piperidinium Acetate with Aromatic Aldehydes^,a

A New 3,5‐Bisporphyrinylpyridine Derivative as a Fluorescent Ratiometric Probe for Zinc Ions

“…During our studies on the structural modification of meso ‐tetraarylporphyrins through a β‐formyl group, we found that the simple reflux of 2‐formyl‐5,10,15,20‐tetraphenylporphyrin 1 in toluene in the presence of piperidine affords the new 3,5‐bisporphyrinylpyridine 2 in 36 % yield (Scheme , a). A literature survey showed that a similar reactivity was reported by Poirier and Burrows for simpler aldehydes like benzaldehyde and analogues 26–28. Based on the proposed mechanism (Scheme S1 in the Supporting Information) namely electrophilic additions to the formyl group and the formation of enamines involving piperidine, and knowing the potentialities of [La(OTf) 3 ] as a Lewis acid even when water is present29 we decided to repeat the condensation in the presence of this reagent.…”

“…A literature survey showed that a similar reactivity was reported by Poirier and Burrows for simpler aldehydes like benzaldehyde and analogues. [26][27][28] Based on the proposed mechanism (Scheme S1 in the Supporting Information) namely electrophilic additions to the formyl group and the formation of enamines involving piperidine, and knowing the potentialities of [La(OTf) 3 ] as a Lewis acid even when water is present [29] we decided to repeat the condensation in the presence of this reagent. Under the new experimental conditions (Scheme 1, b) the desired compound 2 was isolated, after workup and purification, in a comfortable yield of 54 %.…”

Condensation-Based Methods for the C–H Bond Functionalization of Amines

“…Somewhat surprisingly, only sporadic examples of the Rügheimer-Burrows reaction were reported in the following decades. Kameswari and coworkers reported the synthesis of 3-picoline (12), which was obtained as the major product upon passing a mixture of piperidine and trioxane over γ-Al2O3 (Scheme 3). 15 Compared to reactions performed in the presence of acetic acid, which usually proceed in refluxing toluene, this reaction under basic conditions requires over 400 C.…”

“…Somewhat surprisingly, only sporadic examples of the Rügheimer-Burrows reaction were reported in the following decades. Kameswari and co-workers reported the synthesis of 3-picoline (12), which was obtained as the major The Rügheimer-Burrows reaction is also applicable to the synthesis of 4-benzylisoquinoline (15a) from 1,2,3,4tetrahydroisoquinoline (THIQ), as well as 3-benzylquinolines from substituted 1,2,3,4-tetrahydroquinolines (THQ) such as 3-benzyl-6-chloroquinoline ( 16) from 6-chloro-THQ (Scheme 6). Burrows first reported these reactions in 1963.…”

“…The formation of unidentified products was noted. Inspired by the work of Parker and Furst, in the early 1960s, Poirier 12 and Burrows 13,14 independently studied the reaction of piperidinium acetate with benzaldehyde. The structures of the thus obtained products are identical to the product of Rügheimer's reaction.…”