Silane, aluminum complex

SiBrNPCjHs, Phosphorimide bromide, P,P-dimethyl- -(trimethylsilyl)-, 25 70 SiCgHu, Silane, tetramethyl-aluminum complex, 24 92, 94... 

The highly electrophilic cationic bis(8-quinolinolato)aluminum complex 407 enabled Yamamoto and coworkers to perform Mukaiyama-Michael additions of silyl enol ethers to crotonylphosphonates 406. The procedure was not only applicable to enol silanes derived from aryl methyl and alkyl methyl ketones (a-unsubstituted silicon enolates) but also to several cycfic a-disubstituted silyl enol ethers, as illustrated for the derivatives of a-methyl tetralone and indanone 405 in Scheme 5.105. Despite the steric demand of that substitution pattern, the reaction occurred in relatively high chemical yield with varying diastereoselectivity and excellent enantiomeric excess of the major diastereomer. The phosphonate residue was replaced in the course of the workup procedure to give the methyl esters 408. The protocol was extended inter alia to the silyl enol ether of 2,6,6-tetramethylcyclohexanone. The relative and absolute configuration of the products 408 was not elucidated [200]. 

The ionic phosphonates like NTMP are effective hydration inhibitors because they can form an insoluble complex with the oxide surface. They are useful as epoxy adhesive couplers in cases where the adhesive and its curing cycle are compatible with the adsorbed phosphonate molecule. (14) Wedge test results indicate that in two epoxy-aluminum systems studied, certain organosilanes tend to both increase the epoxy-metal bond durability and maintain hydration resistance. The results of anodic polarization experiments further suggest that these silane films are effective against localized pitting. 

We will next consider the case of a lew silica content co-gel. A 5% silica-content silica-alumina was prepared by precipitation of aluminum isdsutoxide and tetraethoxv-silane as described for the silica-free gel. After gelation water was added just sufficient to fill the pore voids of the gel. The added water led to formation of a boehmite-rich hase during recrystallization. After drying at 120 and calcination at 500 0 for 16 hours, a transitional alumina hase is formed with a surface area of 410 m /g and a pore volume of 1.9 oc/g. This silica-alumina had an average pore diameter of 18 nm, similar to the silica-free material discussed previously. Steam treatment of this 18 nm pore diameter silica-alumina at 870°C (1600 ) in 90% H20-10% N2 for 16 hours resulted in a material with surface area of 196 m /g. This surface area is much hi er than expected for an amori ous gel and is consistent with silica enrichment of the outer surface during the recrystallization step vhere water was added to the pores of the amoridious gel. Silica stabilization of bodunite alumina by formation of a surface Aiase complex has been reported in recent work (9). ESCA analysis also indicates silica surface enrichment vhen compared to the amori ous gel. 

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