title: Regioisomeric preferences in the orthomanganation of meta-substituted acetophenones and isopropyl benzoates, and application of iodo-demanganation with iodine chloride to the synthesis of 2-iodo-3-O-substituted and other ortho-iodo arylcarbonyl compounds

authors: Cooney, Janine M.

subjects: Manganese

abstract: Synthesis is reported of regioisomeric ortho-[Mn(CO)4] derivatives of aryl ketones (2-chlorothioxanthen-9-one and 3′,4′-methylenedioxyacetophenone) and esters (isopropyl 3-methoxy- and 3-acetoxy-benzoate), as well as of the single ortho-[Mn(CO)4] products from methyl 4-methoxy- and 3,5-dimethoxy-benzoate. Factors influencing the preference for manganation at the crowded positions ortho to the C=O in meta-substituted aryl ketones and esters are considered. The frequency of the lowest energy metal carbonyl stretching mode is useful in the structural assignment of the regioisomers. Isopropyl 2-iodo-3-methoxy- and 2-iodo-3-acetoxy-benzoates are obtained by reaction of iodine chloride to replace the Mn(CO)4 group at the crowded 2-position of the corresponding orthomanganated 3-O-substituted benzoate esters. ortho-Iodoacetophenones were prepared likewise, without α-iodination, some with iodine in crowded positions (2′-iodo-3′-methoxy-, -3′,4′-methylenedioxy- and -3′,4′,5′-trimethoxy-acetophenone), others with O-protected 2′-hydroxy groups (2′-benzyloxy- and 2′-t-butyldimethylsilyloxy-3′,4′-dimethoxy-6′-iodobenzene and 2′-t-butyldimethylsiloxy-6′-iodobenzene). Potential general synthetic routes to derivatives of 2-iodo-3-hydroxy-, 2-iodo-3,4-dihydroxy-, and 2-iodo-6-hydroxy-aryl carbonyl compounds are indicated. The corresponding routes to 3-iodo-4-acetyl-2,5-dimethylthiophene and 3-iodo-2-acetylthiophene are also reported.

text: Regioisomeric preferences in the orthomanganation of meta-substituted acetophenones and isopropyl benzoates, and application of iodo-demanganation with iodine chloride to the synthesis of 2-iodo-3-O-substituted and other ortho-iodo arylcarbonyl compounds Synthesis is reported of regioisomeric ortho-[Mn(CO)4] derivatives of aryl ketones (2-chlorothioxanthen-9-one and 3′,4′-methylenedioxyacetophenone) and esters (isopropyl 3-methoxy- and 3-acetoxy-benzoate), as well as of the single ortho-[Mn(CO)4] products from methyl 4-methoxy- and 3,5-dimethoxy-benzoate. Factors influencing the preference for manganation at the crowded positions ortho to the C=O in meta-substituted aryl ketones and esters are considered. The frequency of the lowest energy metal carbonyl stretching mode is useful in the structural assignment of the regioisomers. Isopropyl 2-iodo-3-methoxy- and 2-iodo-3-acetoxy-benzoates are obtained by reaction of iodine chloride to replace the Mn(CO)4 group at the crowded 2-position of the corresponding orthomanganated 3-O-substituted benzoate esters. ortho-Iodoacetophenones were prepared likewise, without α-iodination, some with iodine in crowded positions (2′-iodo-3′-methoxy-, -3′,4′-methylenedioxy- and -3′,4′,5′-trimethoxy-acetophenone), others with O-protected 2′-hydroxy groups (2′-benzyloxy- and 2′-t-butyldimethylsilyloxy-3′,4′-dimethoxy-6′-iodobenzene and 2′-t-butyldimethylsiloxy-6′-iodobenzene). Potential general synthetic routes to derivatives of 2-iodo-3-hydroxy-, 2-iodo-3,4-dihydroxy-, and 2-iodo-6-hydroxy-aryl carbonyl compounds are indicated. The corresponding routes to 3-iodo-4-acetyl-2,5-dimethylthiophene and 3-iodo-2-acetylthiophene are also reported.

year: 2001-09-01

title: Ensembles of restricted Hoeffding trees

authors: Bifet, Albert

subjects: design

abstract: The success of simple methods for classification shows that is is often not necessary to model complex attribute interactions to obtain good classification accuracy on practical problems. In this article, we propose to exploit this phenomenon in the data stream context by building an ensemble of Hoeffding trees that are each limited to a small subset of attributes. In this way, each tree is restricted to model interactions between attributes in its corresponding subset. Because it is not known a priori which attribute subsets are relevant for prediction, we build exhaustive ensembles that consider all possible attribute subsets of a given size. As the resulting Hoeffding trees are not all equally important, we weigh them in a suitable manner to obtain accurate classifications. This is done by combining the log-odds of their probability estimates using sigmoid perceptrons, with one perceptron per class. We propose a mechanism for setting the perceptrons' learning rate using the ADWIN change detection method for data streams, and also use ADWIN to reset ensemble members (i.e., Hoeffding trees) when they no longer perform well. Our experiments show that the resulting ensemble classifier outperforms bagging for data streams in terms of accuracy when both are used in conjunction with adaptive naive Bayes Hoeffding trees, at the expense of runtime and memory consumption. We also show that our stacking method can improve the performance of a bagged ensemble.

text: Ensembles of restricted Hoeffding trees The success of simple methods for classification shows that is is often not necessary to model complex attribute interactions to obtain good classification accuracy on practical problems. In this article, we propose to exploit this phenomenon in the data stream context by building an ensemble of Hoeffding trees that are each limited to a small subset of attributes. In this way, each tree is restricted to model interactions between attributes in its corresponding subset. Because it is not known a priori which attribute subsets are relevant for prediction, we build exhaustive ensembles that consider all possible attribute subsets of a given size. As the resulting Hoeffding trees are not all equally important, we weigh them in a suitable manner to obtain accurate classifications. This is done by combining the log-odds of their probability estimates using sigmoid perceptrons, with one perceptron per class. We propose a mechanism for setting the perceptrons' learning rate using the ADWIN change detection method for data streams, and also use ADWIN to reset ensemble members (i.e., Hoeffding trees) when they no longer perform well. Our experiments show that the resulting ensemble classifier outperforms bagging for data streams in terms of accuracy when both are used in conjunction with adaptive naive Bayes Hoeffding trees, at the expense of runtime and memory consumption. We also show that our stacking method can improve the performance of a bagged ensemble.

year: 2012

title: The Aroha block from 1880 onwards

authors: Hart, Philip

abstract: With the discovery of gold in 1880 and the pressure to open the land for mining, there was a need to determine the boundaries of the Ngati Rahiri reserves and to subdivide these amongst the owners. As well, terms for paying goldfields revenue had to be negotiated before the goldfield could be opened, and after its opening the claims of Maori with little or no basis for their claims of ownership had to be investigated. Wairakau reserve, outside the goldfield, was not subdivided until mid-1882, and arguments over the ownership of Tui Pa continued well into the twentieth century. 
At first, sales of Crown land found few takers, especially because the farm sections required draining before they could be developed. Ngati Rahiri reserves were designated as being inalienable, but they could be leased for 21 years, as some portions were, at low rates. Very quickly, officials, who feared Maori would become landless, had to fend off requests to remove restrictions on sale made by owners who in some instances lived far from Te Aroha and who all wanted to obtain money from selling land of little use to them. The indebtedness of some owners led to continued pressure to sell, though often the money they received was wasted. With the fading of the goldfield, miners sought land for farms, and were frustrated at the Crown not purchasing the Ngati Rahiri reserves. 
Land was acquired by the Crown to extend the hot springs domain, and after negotiating improved leases in the Te Aroha township the freehold of this settlement was acquired. Some Maori retained their land, which Pakeha accused them of not improving; Maori requests that the government provide training in farming methods were ignored. By the twentieth century most Ngati Rahiri had become landless, but as many examples illustrate, this was commonly because cash-strapped owners insisted on selling their interests for an immediate financial return.

text: The Aroha block from 1880 onwards With the discovery of gold in 1880 and the pressure to open the land for mining, there was a need to determine the boundaries of the Ngati Rahiri reserves and to subdivide these amongst the owners. As well, terms for paying goldfields revenue had to be negotiated before the goldfield could be opened, and after its opening the claims of Maori with little or no basis for their claims of ownership had to be investigated. Wairakau reserve, outside the goldfield, was not subdivided until mid-1882, and arguments over the ownership of Tui Pa continued well into the twentieth century. 
At first, sales of Crown land found few takers, especially because the farm sections required draining before they could be developed. Ngati Rahiri reserves were designated as being inalienable, but they could be leased for 21 years, as some portions were, at low rates. Very quickly, officials, who feared Maori would become landless, had to fend off requests to remove restrictions on sale made by owners who in some instances lived far from Te Aroha and who all wanted to obtain money from selling land of little use to them. The indebtedness of some owners led to continued pressure to sell, though often the money they received was wasted. With the fading of the goldfield, miners sought land for farms, and were frustrated at the Crown not purchasing the Ngati Rahiri reserves. 
Land was acquired by the Crown to extend the hot springs domain, and after negotiating improved leases in the Te Aroha township the freehold of this settlement was acquired. Some Maori retained their land, which Pakeha accused them of not improving; Maori requests that the government provide training in farming methods were ignored. By the twentieth century most Ngati Rahiri had become landless, but as many examples illustrate, this was commonly because cash-strapped owners insisted on selling their interests for an immediate financial return.

year: 2016