Спиро қосылыстар: құрылымы мен атаулары

Organic molecule with two or more rings sharing a common atom

In organic chemistry, spiro compounds are compounds that have at least two molecular rings with only one common atom. The simplest spiro compounds are bicyclic (having just two rings), or have a bicyclic portion as part of the larger ring system, in either case with the two rings connected through the defining single common atom. The one common atom connecting the participating rings distinguishes spiro compounds from other bicyclics: from isolated ring compounds like biphenyl that have no connecting atoms, from fused ring compounds like decalin having two rings linked by two adjacent atoms, and from bridged ring compounds like norbornane with two rings linked by two non adjacent atoms. ]] Bicyclic ring structures in organic chemistry that have two fully carbocyclic (all carbon) rings connected through just one atom are present both in natural products,

Spiro compounds are considered heterocyclic if the spiro atom or any atom in either ring are not carbon atoms. Cases include the presence of a spiro heteroatom such silicon and nitrogen (but also other Group IVA [14] and other atom types) connecting the rings that have been observed or are under theoretical study;

A common case is the presence of two atoms that are not carbon in one of the rings, with those two rings both attached to the spiro atom; indeed, often the earliest exposure of a chemist in training to a spiro compound is to a heterocyclic form, the ketal (acetal) formed in the protection of ketones by diols and dithiols. An example of this is shown above, in the synthesis of the acetal 1,4 dioxaspiro[4.5]decane from cyclohexanone and ethanediol. In this case, because the four atoms attached to the spiro atom are not all carbons, the spiro atom is not a quaternary carbon. A further example of an acetal formed from a cyclic ketone, except with a dithiol, is the spiro compound spirapril, which has a five membered ring formed from 1,2 ethanedithiol. Again, while the rings could be identical, in the heterocyclic case they are, again, almost always non identical. Once again, the best fit planes to each ring are generally non coplanar to one another (i. e., the rings are not coplanar, despite appearing so in images).

A polyspiro compound is connected by two or more spiroatoms making up three or more rings.

Nomenclature for spiro compounds was first discussed by Adolf von Baeyer in 1900. The prefix spiro denotes two rings with a spiro junction. The main method of systematic nomenclature is to follow with square brackets containing the number of atoms in the smaller ring then the number of atoms in the larger ring, separated by a period, in each case excluding the spiroatom (the atom by which the two rings are bonded) itself. Position numbering starts with an atom of the smaller ring adjacent to the spiroatom around the atoms of that ring, then the spiroatom itself, then around the atoms of the larger ring. For example, compound A in the image is called 1 bromo 3 chlorospiro[4.5]decan 7 ol, and compound B is called 1 bromo 3 chlorospiro[3.6]decan 7 ol.

Spiranes can be chiral, in three distinct ways.]. Initially, one of the carbinol moieties is protonated, allowing water to leave, and yielding the corresponding carbocation (second structure, first row); this intermediate then undergoes a bond migration, resulting in ring expansion of the adjacent ring, with deprotionation unmasking the ketone functional group to complete the first line of the mechanism. This first product, a spirobicyclic ketone, is a spiro compound in its own right, and yields the further spiro carbinol and the alicyclic spiro hydrocarbon after two further reduction reactions. First, reduction of the carbonyl that ends the mechanism's first line provides the spiro carbinol starting material of the second line, which is needed for reduction to the alkane (shown). This latter reduction is accomplished using lithium aluminium hydride (LiAlH4), via the alcohol tosylate (formed using tosyl chloride). Hence this three reaction sequence provides three spiro compounds (ketone, alcohol, and alkane), of possible research or practical use. is a chemical compound, typically an organic compound, that presents a twisted structure of two or more rings (a ring system), in which 2 or 3 rings are linked together by one common atom, examples of which are shown at right.