Remote active

You can quickly identify these plant sections by reviewing process flow diagrams and valving arrangements. Isolation points are defined by control valves or powered block valves that can be remotely activated. Process hazard analysis techniques help you identify the maximum credible accident scenarios. (Note that manual valves should not be considered reliable isolation points unless they are located to be accessible following a major accident. However, remotely-activated valves can only be considered reliable isolation points if there are adequate reliability engineering and maintenance programs in place.)... 

Interactions refers to any jobs, tasks, or operations carried out by people who could directly or indirectly cause the hazard to be released. Direct interactions with the plant might involve breaking open pipework, opening reactors, etc. Indirect interactions would include remote activation of valves from a control room, or the performance of maintenance on critical plant items. Errors that might occur during these interactions could allow the harm potential to be released. This could occur directly (for example, a worker could be overcome by a chlorine release if an incorrect valve line-up was made) or indirectly (for example, if a pump bearing in a critical cooling circuit was not lubricated, as in the example in Chapter 1). The procedure as described above... 

Automatic or remotely activated isolation valves provided to limit quantities of materials that are released... 

Conjugation between the imino and acyl [121], or nitrile (in complex 1.47) [122] moieties permitted the remote activation of nickel. Another catalyst (1.48) exhibiting coordination via an alkenyl moiety is noteworthy because of its sterically small size, which should prohibit the production of high molecular weight polymers [123], This is believed to be possible because of the catalyst s unique electronic properties. As bulkier imino-aryl substituents are introduced, polymerization activity and polymer molecular weight increases, as expected [124],... 

When more than one pump is installed, they should be coordinated to start in sequence, since immediate start up of all pumps may not be necessary and could cause damage to the system. Depending on the number of pumps available, they can be set to startup on sequentially decreasing fire main set points. All fire water pumps should be able to be started from remote activation switches located in manned control rooms. 

Carbamate glycosyl donors are another useful class of compounds, which pre sent significant variability in chemical structures (Scheme 3.24). In an early example by Kunz and Zimmer, the N-allyl carbamate donors were used in a remote activation protocol to furnish pyranoside and furanoside products. In this reaction, the N-allyl carbamate donor 146 is activated with dimethyl methylthiosulfonium... 

Other types of remote activation are illustrated in the syntheses of kreysigine [260] and A-methyllaurotetanine [261]. 

The imidazole-l-sulfonate (imidazylate, lmz) group was a designed leaving group for Sn2 displacement reactions by virtue of its inherent structure [68]. It represents a different notion of reactivity because, in addition to the inherent sulfonate-type character, its reactivity can be enhanced by remote activation involving a nitrogen atom (Scheme 5). 

Chemistry of the glycoside linkage. Exceptionally fast and efficient formation of glycosides by remote activation, Carbohydr. Res. 80 07 (1980). (e) K. Wiesner, T. Y. R. Tsai, and H. Jiu, On cardioactive steroids. XVI. Stereoselective P-glycosylation of digitoxose the synthesis of digitoxin, Helv. Chim. Acta 60 300 (1985). (f) R. B. Woodward (and 48 collaborators), Asymmetric total synthesis of erythromycin. 3. Total synthesis of erythromycin, J. Am Chem. Soc. 103 3215 (1981). (g) P. G. M. Wuts and S. S. Bigelow, Total synthesis of oleandrose and the avermecin disaccharide, benzyl ot-L-oleandrosyl-ot-L-4-acetOxyoleandroside, J. Org. Chem. 43 3489 (1983). 

S. Hanessian, C. Bacquet, and N. Lehong, Chemistry of the glycosidic linkage. Exceptionally fast and efficient formation of glycosides by remote activation, Carbohydr. Res. 80 017 (1980). 

Glycoside Synthesis Based on the Remote Activation Concept An Overview... 

The first generation of an O-unprotected glycosyl donor that could be activated based on the remote activation concept was exemplified by 2-pyridylthio p-D-glucopyranoside 1 [10], which could be easily prepared from acetobromoglucose [11]. Treatment of 1 with a variety of alcohols in the presence of mercuric nitrate in acetonitrile solution led, within a few minutes, to the corresponding O-glycosides, with isolated yields and a/p ratios varying from methanol (70 30, 95%), to 2-propanol (62 38 77%), and cyclohexanol (51 49, 75%) Scheme 2. Identical results were obtained when 2-pyrimidinylthio p-D-... 

In spite of the successful implementation of the concept of remote activation of an anomeric 2-pyridylthio group, there emerged various issues and questions. The absence of self-condensation products could be ascribed to the use of excess acceptor in all cases, and possibly to the coordination of the mercuric salt to the free hydroxy groups of the donor, thereby diminishing their reactivity. However, the necessity to use an excess of acceptor (> 5 eq), the formation of anomeric mixtures of glycosides, and the use of a mercuric salt, limited the generality of this method of glycoside synthesis. 

Several other glycosidation methods can also be considered as proceeding by remote activation. For example, treatment of 0-benzyl glycosyl trichloroacetimidates with BFj-EtjO [2 see also Chap. 11], or 0-benzyl pentenyl glycosides with NBS [19 see also Chap. 13] leads to activation at an atom not directly attached to the anomeric center. 

Oligosaccharide Synthesis by Remote Activation O-Protected 3-Methoxy-2-pyridyloxy (MOP) Glycosyl Donors... 

Scheme 1 The design of glycosyl 2-pyridylcarbonate or glycosyl 2-thiopyridylcarbonate (TOP-CAT) donors based on the remote activation concept.

K. Koidc, M. Ohno, and S. Kobayashi, A new glycosylation reaction based on a remote activation concept Glycosyl 2-pyridinecarboxylate as a novel glycosyl donor. Tetrahedron Lett. 32 7065 (1991). 

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