Premium
Hetero‐ Diels‐Alder and Cheletropic Additions of Sulfur Dioxide to 1,2‐Dimethylidenecycloalkanes. Determination of Thermochemical and Kinetics Parameters for Reactions in Solution and Comparison with Estimates From Quantum Calculations
Author(s) -
Monnat Frédéric,
Vogel Pierre,
Sordo José Ángel
Publication year - 2002
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/1522-2675(200203)85:3<712::aid-hlca712>3.0.co;2-5
Subject(s) - chemistry , thiophene , kinetics , sulfur dioxide , catalysis , oxide , transition state , density functional theory , computational chemistry , medicinal chemistry , thermodynamics , organic chemistry , physics , quantum mechanics
Below −60° and without catalyst, 1,2‐dimethylidenecyclopentane ( 16 ), 1,2‐dimethylidenecyclohexane ( 13 ), 1,2‐dimethylidenecycloheptane ( 17 ), and 1,2‐dimethylidenecyclooctane ( 18 ) add to sulfur dioxide in the hetero‐ Diels‐Alder mode, giving the corresponding sultines 4,5,6,7‐tetrahydro‐1 H ‐cyclopent[ d ][1,2]oxathiin 3‐oxide ( 19 ), 1,4,5,6,7,8‐hexahydro‐2,3‐benzoxathiin 3‐oxide ( 14 ), 4,5,6,7,8,9‐hexahydro‐1 H ‐cyclohept[ d ][1,2]oxathiin 3‐oxide ( 20 ), and 1,4,5,6,7,8,9,10‐octahydrocyclooct[ d ][1,2]oxathiin 3‐oxide ( 21 ), respectively. Above −40°, the sultines are isomerized into the corresponding sulfolenes 3,4,5,6‐tetrahydro‐1 H ‐cyclopenta[ c ]thiophene 2,2‐dioxide ( 22 ), 1,3,4,5,6,7‐hexahydrobenzo[ c ]thiophene 2,2‐dioxide ( 15 ), 3,4,5,6,7,8‐hexahydro‐1 H ‐cyclohepta[ c ]thiophene 2,2‐dioxide ( 23 ), and 1,3,4,5,6,7,8,9‐octahydrocycloocta[ c ]thiophene 2,2‐dioxide ( 24 ). Kinetics and thermodynamics data were collected for these reactions. The sultines are ca. 10 kcal/mol Diels‐Alder additions (Δ H ≠ ( 16 −36±3 cal mol −1 K −1 ) in agreement with third‐order rate laws that imply that two molecules of SO 2 intervene in the transition states of these cycloadditions. Similar observations were made for the cheletropic additions of SO 2 . Attempts to simulate the thermodynamics and kinetics parameters of the reactions of SO 2 with dienes 16 and 13 by density‐functional theory (DFT) suggest that the calculations require an appropriate number of polarization functions in the basis set employed. A satisfactory recipe to compute the SO 2 additions to large dienes can be: B3LYP/6‐31G(d) geometry optimizations followed by B3LYP/6‐31+G(2df,p) single‐point calculations or G2(MP2,SVP) estimates on the B3LYP/6‐31G(d) geometries.