Ketones, 2-amino-1 -alkenyl synthesis

Carbon monoxide rapidly inserts into the carbon—zirconium bond of alkyl- and alkenyl-zirconocene chlorides at low temperature with retention of configuration at carbon to give acylzirconocene chlorides 17 (Scheme 3.5). Acylzirconocene chlorides have found utility in synthesis, as described elsewhere in this volume [17]. Lewis acid catalyzed additions to enones, aldehydes, and imines, yielding a-keto allylic alcohols, a-hydroxy ketones, and a-amino ketones, respectively [18], and palladium-catalyzed addition to alkyl/aryl halides and a,[5-ynones [19] are examples. The acyl complex 18 formed by the insertion of carbon monoxide into dialkyl, alkylaryl, or diaryl zirconocenes may rearrange to a r 2-ketone complex 19 either thermally (particularly when R1 = R2 = Ph) or on addition of a Lewis acid [5,20,21]. The rearrangement proceeds through the less stable... 

The synthesis of 2-aminobutadienes from ketones is somewhat limited due to difficult control of /Z-stereochemistry. [27] Therefore, the catalytic aminomercuration of3-alkenyl-l-ynes 4 was a significant improvement of the synthesis of 2-amino-l,3-butadienes 5 (yields 49-75 %). [28] The catalytic aminomercuration of 4-ethoxy-3-alkenyl-1-ynes even leads to electronrich and highly reactive 1,3-diamino-1,3-butadiens which undergo a great variety of cycloadditions. [29] Scheme 2 shows the reaction for a general example (for R = H two secondary amines can add to the enine 4 to yield 6). The method can easily be extended to the preparation of chiral 2-amino-1,3-butadienes by addition of chiral amines [e. g. (5)-2-methoxymethylpyr-rolidine (SMP) [27]]. 

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