Ketones, condensation with organometallic reagents

The presence of unsaturation in the side chain is also compatible with antihistaminic activity. Mannich condensation of p-chloroacetophenone with formaldehyde and pyrollidine affords the amino ketone, 109. Reaction with an organometallic reagent from 2-bromopyridine gives 110. Dehydration leads to triproli-dine (111). ... 

Several other preparative methods, involving the condensation of (i) N-(trimethylsUyl)phosphinimines and carbonyl compounds and (ii) organometallic reagents with nitriles followed by quenching with chlorotrimethylsilane, have been used for the preparation of other aldehyde- and ketone-derived... 

One of the most effective ways of preparing enantiomerically pure secondary amines is the addition of organometallic reagents to chiral sul fmimines, which are prepared by the condensation of an aldehyde (or ketone) with a sulfinamide. The preparation of /-butyl sulfinamide had been problematic, but the synthesis (and supplies) now seems to be more reliable. 

Ketones can be prepared starting from esters via the intermediate 2-acylbenzothiazoles (511) which are easily obtained by condensation with 2-lithiobenzothiazole (230). The reaction of these compounds with an organometallic reagent and subsequent quaternization of the heterocyclic ring affords the A -methylbenzothiazolium salts (512) which upon treatment with a base yield the corresponding ketones (Scheme 120) <91BCJ3256>. 

In general, the trans-l-alkenyl organometallic reagents are prepared from the corresponding terminal acetylene (e.g., 77 and 79, Scheme 14). These intermediates are available by condensation of the appropriate aldehyde or ketone with ethynyl... 

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