Stabase adducts

Allylic amines. The stabase adduct (1) of 2-chloroallylamine couples with Grignard reagents in the presence of NiCl2(dppp), dppp = (CfiH )2P(CH2),P(C6H5)2, to form, after deprotection, allylic amines. 

Pyrrolidines. The Grignard reagent 2, obtained from 3-bromopropylamine protected as the stabase adduct with 1, reacts with the N-methoxy-N-methyl amides 3 (11, 201-202) to form an intermediate ketone that cyclizes to an imine on liberation of the free primary amino group. Reduction of the imine results in a 2-substituted pyrrolidine (4). 

Recently silicon-based protection has matured into a new Ix oad area of protecting group chemistry (see Section 3.1.3.2) and amines can also be conveniently blocked with appropriate silicon reagents. In organometallic syntheses, e.g. in the alkylation of amino acid enolates, the so-called stabase adducts (30) serve to temporarily protect the a-amino group (Scheme 21). In the absence of hard nucleophiles, in particular of 0-nucleophiles, the Si—N bonds are stable, but deprotection is readily effected in the presence of water and acids. 

Protection of primary amines. Primary amines form the cyclic adducts 2 ( Stabase adducts ) on reaction with 1 and a base (triethylamine for amines with pK 10-11, tt-butyllithium for less basic amines). The adducts are stable to n- and. sec-BuLi (-25°), LDA, H20, CH3OH, KF, and NaHC03 but unstable to HOAc, HC1, KOH, and NaBH. ... 

Sodium trithiocarbonate, 369-370 Spiroannelation, 240, 266-267, 443 Spiro [4.5 ] decadienones, 443 Spiro [4.5 ] decenes, 266-267 Spiro-[4.5]decenones, 100 Spirolactones, 8, 155,192 Stabase adducts, 140 Stannic chloride, 370-373 Stannous chloride-Silver perchlorate, 374 Stannous fluoride, 374 Stannoxanes, 124 Stemodin, 169... 

Unsaturated a-Amino-acids.—Protection of the primary amino-group of ethyl glycinate as a stabase adduct, renders it stable to organolithium reagents hence the lithiated species (196) is readily prepared. Subsequent conversion into racemic 2-aminopent-4-ynoic acid (197) and vinyl glycine (198) is easily achieved (Scheme 90). ... 

Scheme 73 STABASE and l,l,3,3-Tetramethyl-l,3-disilaisoindoline Adducts of Amino Acid Esters " ...

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