Carbonylation thiocarbonylation

Cyclic Carhene Complexes. The reaction of aziridines with carbonyl, thiocarbonyl, or isonitrile ligands in Mn, Re, Fe, Ru, Pd, or Pt complexes leads to formation of cycHc carhene complexes (324—331). 

Instead of CDI, carbonyl-, thiocarbonyl- or sulfinyldibenzotriazole have also been used for formation of the nucleoside phosphoric azolide.1551... 

Reactions Involving Carbonyl, Thiocarbonyl, or Methylene at the 3-Position... 

D. CARBONYL(THIOCARBONYL)TRIS(TRIPHENYL-PHOSPHINE)OSMIUM(O)6... 

In principle, when carbonyl, thiocarbonyl or iminoyl groups react with a nucleophile, a covalent bond is formed and the carbon hybridization changes from sp2 to sp3 (equilibrium 22). 

G. R. Clark, K. Marsden, W. R. Roper, and L. J. Wright, Carbonyl, Thiocarbonyl, Selenocarbonyl, and Tellurocarbonyl Complexes Derived from a Dihalocarbene Complex of Osmium, J. Am. Chem. Soc. 102, 1206-1207 (1980). 

Few binary metal thiocarbonyls are known. Nickel tetrathiocarbonyl, Ni(CS)4, is unstable at room temperature, but many mixed carbonyl-thiocarbonyl complexes are stable and have properties similar to those of the parent carbonyl compounds. Examples are Cr(CO)5(CS), ( QH6)Cr(CO)2(CS),109 Cr(CO)3(CS)[P(OPh)3]2,° and Fe(CO)4(CS). 

Enophiles may include carbonyls, thiocarbonyls, imines, alkenes and alkynes. When the carbonyl is an enophile, the reaction is called a carbonyl ene reaction. The enol form of an unsaturated ketone may serve as an ene in an intermolecular ene reaction known as the Conia-ene reaction. Ene reactions proceed best when the enophilic double bond is electron deficient. Hydrogen is the most common atom transferred in an ene reaction. Other atoms or groups may, however, participate in ene-like transformations. 

In contrast to the various methods that have been developed for the synthesis of A2- and A3-triazolines, there appears to be no general synthetic routes to A -l, 2,4-triazolines (172). Of late, the latter have generated interest as potential sources of azomethine ylides, in analogy with oxa- and thiadiazolines that yield carbonyl (thiocarbonyl) ylides upon thermolysis under mild conditions (Scheme 51) (76T2165 85MI2). 

If the group next to the selenium atom is a carbonyl, thiocarbonyl, or selenocarbonyl [selenoesters C-Se-C(=X)-C X = O, S, Se], the selenium atom is deshielded and its chemical shift becomes larger 3-values between 400 and 1100 may occur for example 126-128 (Scheme 22) This can be rationalized qualitatively by assuming a considerable contribution of the dipolar mesomeric form (see 126). 

Even though there are obvious difficulties with tautomerism, which can sometimes interrelate the above rankings, carbonyl, thiocarbonyl, and imino derivatives of each type will normally be dealt with last. 

A 47r-electrocyclization route to (323) is shown in Scheme 17. The initial adduct (321) between (319 NR = morpholino, pyrrolidino, or piperidino) and a-bromoacetophenone (320) yields a transient carbonyl-thiocarbonyl ylide (322), which undergoes electrocyclization to the thiiran product (323). 

The dipolarophile may contain any type of double or triple bond, e.g., an ethylenic, acetylenic, carbonyl, thiocarbonyl, or nitrile group. Compounds... 

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