Aldehydes continued aromatic

This method is especially useful for construction of a quinoline library (Scheme 6) [19]. The procedure is very simple it involves just mixing the catalyst (PA-Sc-TAD), an aldehyde, an aromatic amine, and an alkene (alkyne). After filtration, the filtrates are concentrated to give almost pure quinoline derivatives in most cases. Dehydrating agents such as MS 4A, MgS04, etc. are not necessary. It is noted that PA-Sc-TAD is water-tolerant and that substrates having water of crystallization can be used directly. PA-Sc-TAD can be easily recovered and continuous use is possible without any loss of activity (Scheme 7). 

Surprisingly the water consumption of a starter battery, provided it contains anti-monial alloys, is affected by the separator. Some cellulosic separators as well as specially developed polyethylene separators (e.g., DARAMIC V [76]) are able to decrease the water consumption significantly. The electrochemical processes involved are rather complex and a detailed description is beyond the scope of this chapter. Briefly, the basic principle behind the reduction of water loss by separators is their continuous release of specific organic molecules, e.g., aromatic aldehydes, which... 

Another SBU with open metal sites is the tri-p-oxo carboxylate cluster (see Section 4.2.2 and Figure 4.2). The tri-p-oxo Fe " clusters in MIL-100 are able to catalyze Friedel-Crafts benzylation reactions [44]. The tri-p-oxo Cr " clusters of MIL-101 are active for the cyanosilylation of benzaldehyde. This reaction is a popular test reaction in the MOF Hterature as a probe for catalytic activity an example has already been given above for [Cu3(BTC)2] [15]. In fact, the very first demonstration of the catalytic potential of MOFs had aheady been given in 1994 for a two-dimensional Cd bipyridine lattice that catalyzes the cyanosilylation of aldehydes [56]. A continuation of this work in 2004 for reactions with imines showed that the hydrophobic surroundings of the framework enhance the reaction in comparison with homogeneous Cd(pyridine) complexes [57]. The activity of MIL-lOl(Cr) is much higher than that of the Cd lattices, but in subsequent reaction rans the activity decreases [58]. A MOF with two different types of open Mn sites with pores of 7 and 10 A catalyzes the cyanosilylation of aromatic aldehydes and ketones with a remarkable reactant shape selectivity. This MOF also catalyzes the more demanding Mukaiyama-aldol reaction [59]. 

The thio-Wittig reaction, like the Wittig itself, may involve (thia)phosphetane or betaine-type structures as intermediates. A combined experimental and theoretical study over a wide range of conditions and of substrates (aliphatic vs aromatic, aldehyde- vs ketone-derived) suggests a mechanistic continuity, with solvent polarity and substrate electronic effects being the main influences on the transition from one mechanism to another. ... 

JOU2236). In the case of TCE 33 the cyclization proceeds without a catalyst on short heating (73CB914). However, continuous heating leads to bis(6-hydroxy-2,4-dioxo-l,2,3,4-tetrahydropyrimidin-5-yl)malononi-trile. Modern modification involves a three-component reaction of aromatic aldehyde, malononitrile, and barbituric acid with solvent-free conditions under microwave irradiation (4-8 min, 70-95%) (03TL8307). 

In addition to the direct electrosyntheses, work also continued on the well known indirect electrosyntheses of aromatic aldehydes by in-cell and ex-cell regeneration of redox systems, such as Mn2+/Mn3+ 193 194> and Ce3+/Ce4+ 195). 

The use of bifunctional thiourea-substituted cinchona alkaloid derivatives has continued to gamer interest, with the Deng laboratory reporting the use of a 6 -thiourea-substituted cinchona derivative for both the Mannich reactions of malo-nates with imines [136] and the Friedel-Crafts reactions of imines with indoles [137]. In both reports, a catalyst loading of 10-20 mol% provided the desired products in almost uniformly high yields and high enantioselectivities. Thiourea-substituted cinchona derivatives have also been used for the enantioselective aza-Henry reactions of aldimines [138] and the enantioselective Henry reactions of nitromethane with aromatic aldehydes [139]. 

Aldehydes and ketones react with aromatic compounds in the presence of Bransted or Lewis acids. The actual electrophile is the carboxonium ion formed in an equilibrium reaction by protonation or complexation, respectively. The primary product is a substituted benzyl alcohol, which, however, is not stable and easily forms a benzyl cation. The latter continues to react further, either via an SN1 or an El reaction. Thereby, the following overall functionalizations are realized Ar—H —> Ar—C-Nu or Ar—H — Ar—C=C. 

---