Organometallic compounds from alkenes

It has been demonstrated that visible light irradiation of the absorption band of AcrH + in the presence of organometallic compounds and alkenes and alkylbenzenes in MeCN results in efficient C-C bond formation between these electron donors and AcrH+ via photoinduced electron transfer from the donors to the singlet excited state of AcrH+ to yield the alkylated or allylated adducts selectively [89-91], The AcrH+ is also photoreduced by ethylbenzene and other alkylbenzenes to yield the corresponding 9-substituted-10-methyl-9,10-dihydroacridine [92] ... 

A review on the developments in Pd-catalysed oxidative Heck reactions of organometallic compounds with alkenes emphasized that organometallic compounds derived from Group HI to Group VI are efficient substrates for the oxidative Heck reaction. The article discussed the mechanisms of several such studies. ... 

Alkenes frequently have two kinds of C—H bonds, vinyl and allyl, that are generally more acidic than the C—H bonds of saturated alkanes. Quantitative measures of acidity are related to the chemistry of the corresponding carbanions and carbanion salts or organometallic compounds. Several methods have been used for the study of anions in the gas phase1. For many acids it is possible to measure equilibrium constants for equilibria of the type in equation 1. From such equilibrium constants with compounds RH of independently known gas-phase acidity, it has been possible to determine the acidities of a wide range of compounds2. 

A concise collection of some modem methods of radical formation via rupture of C-E, C-G and C-A bonds, as well as from alkenes and cyclopropanes, by metals, organometallic hydrides, and photochemical and electrochemical means, are given in the last Chapter of Giese s book [28]. For some examples of radical generation and reactions leading to cyclic and polycyclic compounds see next Chapter (Heading 6.1.3). 

By analogy with allylic organometallic compounds (see Section . ), the possibility of achieving intramolecular related zinc-ene reactions involving allenylzinc species acting as ene-components has been investigated. Such reactions benefit from favorable thermodynamics and were thus expected to proceed more readily than the related intermolecular additions of allenylzincs to alkynes or alkenes. 

The radical anions of carbonyl groups can also be generated via PET from activated alkenes, e.g. allylic silanes or stannanes. Triplet excited aromatic ketones, a-dicarbonyls and Michael systems are suitable substrates for oxidizing allylic Group 14 organometallic compounds with subsequent formation of homoallylic alcohols or S-allylated ketones (Scheme 32) [120-122]. 

In the absence of a strong acid, photoinduced electron transfer from RH (alkyl-benzenes [276] and alkenes [277]) to the singlet excited state of AcrH+ ( AcrH+ ) is reported to lead to formation of the alkylated or ally la ted adducts, 9-R-lO-methyl-9,10-dihydroacridine (AcrHR). Photoinduced electron transfer form a variety of organometallic compounds (RM) also gave the same type of adduct, AcrHR [278-282]. In the presence of HCIO4 (l.2 M), however, the photooxygenation of ethylbenzene to 1-phenylethanol occurs as shown in Eq. 26 ... 

Alkenes, arenes and other unsaturated molecules attach to central atoms, using some or all of their multiply bonded atoms, to give organometallic complexes. While there are many similarities between the nomenclature of coordination and organometallic compounds, the latter differ from the former in clearly definable ways. Organometallic complexes are therefore treated separately in Chapter IR-10. 

These problems may be avoided by making an organometallic compound [often of Cu(I) or Mg(II)] from the halide intended to become the palladium a-complex and to use another vinyl halide as the electrophile. Palladium prefers to take out a halide rather than a hydrogen atom in the P-elimination step and all three problems disappear. In the synthesis of this T, Z-dicnc 134, we prefer to use a Pd a-complex for the Z-alkene part 136 and a vinyl iodide 135 for the E-alkene. 

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