Pyrophoric reagent

Caution Part A must be conducted in a hood, due to the noxious odor of dimethyl sulfide. In Pari B, the usual precautions associated with the pyrophoric reagent Raney nickel must be observed (see Note 8). 

Nickel boride (prepared by adding NaBH4 to nickel chloride in methanol - THF) is an efficient, non-pyrophoric reagent for the desulfurization of benzo[ Jthiophene and dibenzothiophene (90CC819, 92JOC1986). The reaction proceeds under very mild conditions and is probably mediated by nickel hydride. 

The preparation of gallium arsenide is a dangerous process employing two pyrophoric reagents (4.3) 129... 

Handling. Alkylaluminum compounds are highly reactive to air and moisture. A full face shield and leather gloves are essential. Contact with flammable solvents should be avoided. Harney et al. have described in detail suitable apparatus and techniques for handling this and other pyrophoric reagents. 

Some pyrophoric reagents such as ferf-butyllithium are purchased as soluAons in Aammable solvents such as hexane. Should the pyrophoric compound be exposed to air it can ignite and catch the available fuel (i.e., hexane) on Are. An incident that illusAates this possibility is found in Incident 7.3.5.1. 

The Seeberger group reported a microflow synthesis of amides that used a highly pyrophoric reagent trimethylaluminum (Scheme 5.28) [39]. A simple... 

ButyUithium is available as a 15—20 wt % solution in //-pentane or heptane. Noticeable decomposition occurs after alb reflux in heptane (bp 98.4°C) but not after a 15 min reflux in ben2ene (bp 80.1°C) or hexane (bp 68°C). /-ButyUithium in pentane or heptane is more stable than //-butyUithium in hexane (125). Solutions of /-butyUithium in pentane and heptane are flammable Hquids and are considered pyrophoric. The /-butyl compound is more reactive than either the n- and sec-huty. Di-//-butylether is cleaved by /-butyUithium in 4—5 h at 25°C, compared to the 2 d for j iZ-butyUithium and 32 d for //-butyUithium (126). /-ButyUithium can be assayed by aU of the techniques used for //-butyUithium. /-ButyUithium is a useful reagent in syntheses where the high reactivity of the carbon—lithium bond and smaU si2e of the lithium atom promote the synthesis of stericaUy hindered compounds, eg,... 

Although phosphine [7803-51-2] was discovered over 200 years ago ia 1783 by the French chemist Gingembre, derivatives of this toxic and pyrophoric gas were not manufactured on an industrial scale until the mid- to late 1970s. Commercial production was only possible after the development of practical, economic processes for phosphine manufacture which were patented in 1961 (1) and 1962 (2). This article describes both of these processes briefly but more focus is given to the preparation of a number of novel phosphine derivatives used in a wide variety of important commercial appHcations, for example, as flame retardants (qv), flotation collectors, biocides, solvent extraction reagents, phase-transfer catalysts, and uv photoinitiators. 

The purple color seems to be indicative of a satisfactory reduction. When the color is light or no color develops, the yield is usually poor. Sometimes no reaction occurs. In this instance it is best to discard all residues (pyrophoric) carefully and start over with scrupulous attention to dryness of all apparatus and reagents. 

Caution Diethylzinc, which is used in Part B of this procedure, is highly pyrophoric. Accordingly this reagent must be kept under a nitrogen atmosphere, and exposure to air must be avoided during transfers. 

Immediately pyrophoric in air, and explosive decomposition with aqueous reagents. The sodium salt is similar. 

Lack of cooling during preparation of the Simmons-Smith organozinc reagent caused the reaction to erupt. The possibly pyrophoric nature of organozinc compounds and the presence of ether presents a severe fire hazard [1]. An alternative, safer method of activating the zinc for the reaction involves use of ultrasonic irradiation rather than the copper-zinc couple [2]. 

The advantages of this reagent are its straightfonvard synthesis and relative air stability. The previous procedure for the synthesis of dimethyltitanocene used methyllithium in diethyl ether, which is unsuitable for large scale operations because of its extreme pyrophoricity. In addition, the method isolated the compound as a crystalline solid, which the submitters have found to be very unstable. The method described here addresses both of these concerns, and can be used to prepare multiple kilograms of the reagent. 

Neat tripropylaluminum of 96% purity was supplied in a metal cylinder from Toyo Stauffer Chemical Company, Ltd. (Japan). This reagent is contaminated by 1.2% of triethylaluminura, 2.2% of triisobutylaluminum, and other compounds. Neat tripropylaluminum is also available from Aldrich Chemical Company, Inc. Since neat tripropylaluminum is pyrophoric and reacts violently with oxygen and water, the syringe should be washed with hexane immediately after addition. 

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