Alkyl block metal

Propiolaldehyde diethyl acetal has found numerous synthetic applications in the literature which may be briefly summarized. The compound has been utilized in the synthesis of unsaturated and polyunsaturated acetals and aldehydes by alkylation of metal-lated derivatives, " by Cadiot-Chodkiewicz coupling with halo acetylenes, " and by reaction with organocuprates. Syntheses of heterocyclic compounds including pyrazoles, isoxazoles, triazoles, and pyrimidines have employed this three-carbon building block. Propiolaldehyde diethyl acetal has also been put to use in the synthesis of such natural products as polyacetylenes " and steroids. ... 

III. Terminal Alkyl Derivatives of the s- and p-Block Metals Supported by Poly(pyrazolyl)borato Ligation... 

Oxathiolane 2,2-dioxide undergoes metallation with n-butyllithium as expected at the 3-position (81JOC101). The anion may be alkylated with alkyl halides or carbonyl compounds. The isomeric 1,3-oxathiolane 3,3-dioxides also undergo metallation ortho to the sulfone and, when the 4-position is blocked, metallation at the 2-position may be used as an efficient conversion of alkyl halides into aldehydes as shown in Scheme 22 (79TL3375). 

Pure alkyl transition metal complexes are rare, owing to the -Elimination decay mechanism. An effective strategy to prepare such compounds must therefore aim at blocking possible decomposition pathways. Neopentyl is void of hydrogen in the jS-position, and neopentyl... 

Alkyl, Hydride, and Related Bis(trimethylsilyl)amide Derivatives of the 4f- and 5f- Block Metals... 

The p-block metal alkoxides construct the second group. Chukicheva et al. have effectively used aluminum phenoxide and isopropoxide for the alkylation of phenol by borneol, 85 and its stereoisomer, iso-borneol, 86 [60]. It was not seen any special chemo- or enantioselectivity with this catalytic systems. 

In 1848, Edward Frankland attempted to prepare free ethyl radicals by the reaction of EtI with metallic zinc. Instead, he became the founder of organometallic chemistry by showing that the colorless liquid formed was diethylzinc, the first compound known to contain a metal-carbon bond. Victor Grignard s organomagnesium halides of 1900 made organometallic compounds indispensable in organic chemistry. Pope and Peachey s MesPtI (1909) was an early but isolated example of a d-block metal alkyl. 

Main Group alkyls can also (3-eliminate (e.g., Eq. 3.2), but this usually happens much more slowly. The reason for this difference is believed to be the greater ability of d-block metals to stabilize the transition states involved. We shall see shortly how in rare cases stable complexes exist in which transition metals stabilize what appear to be intermediate forms between simple alkyls and the hydride alkene product of (3 elimination. 

In her studies on the /-block metals, Patricia Watson found a remarkable system in which successive alkene insertions into a Lu—R bond can be observed step by step (Eq. 11.62). Not only do the alkenes insert, but the reverse reaction, P elimination of an alkyl group, as well as the usual p elimination of a hydrogen, are also observed. For the d-block this p elimination of an alkvl erouo would normally not be possible it is probably the larger M—R... 

When one begins to consider structural parameters (and indeed chemistry) of later d-block metal aryloxides one is confronted with a different situation. This is highlighted by the values of Ao,c calculated for later transition metal alkyl, aryloxide compounds (Table 6.4). It can be seen that values range from close to zero to positive numbers, Le. in some compounds the M-OAr bond lengths exceed M-C(alkyl) bond lengths This is a dramatically different picture from that seen for early transition metal compounds. 

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