OZONOLYSES OF INDENE AND OF 1-ALKYL-SUBSTITUTED AND 1,1-DIALKYL-SUBSTITUTED INDENES IN PROTIC SOLVENTS - REMARKABLE EFFECTS OF THE SUBSTITUENT STERIC BULK AND THE SOLVENT NUCLEOPHILICITY ON THE DIRECTION OF CLEAVAGE OF THE PRIMARY OZONIDES AND ON THE MODE OF CAPTURE OF THE CARBONYL OXIDE INTERMEDIATES BY THE SOLVENTS

Ozonolyses of indene (1a) and of 1-alkyl- and 1,1-dialkyl-substituted indenes 1b-h in protic solvents including methanol, 2-propanol, and tr ifluoroethanol revealed that (i) two types of the solvent-derived prod ucts, a hemiperacetal and/or an isochroman derivative, are produced de pending on the nucleophilicity of the solvent and the steric bulk of t he alkyl substituent(s), and (ii) the regiochemistry of the fragmentat ion of a primary ozonide is a marked function of the nature of the 1-a lkyl-substituent. In the case ofindene (1a) and 1-substituted indenes 1b-e, both possible modes of primary ozonide cleavage operate competit ively yielding two carbonyl oxide intermediates in roughly equal amoun ts, whereas in the case of 1,1-dialkyl-substituted indenes 1f-h the co ntribution of the less-hindered carbonyl oxide predominates.